This is going to be my final reply to this topic and I want to address quite a bit of what you are asking for, offer some currently available "unique" playstyles, and end with my own recommendations.
There are two very different MMORPG balancing philosophies, the more modern approach of, keep everything level so that it will be easier to project how players will clear content and progress, and the more archaic philosophy of, if it fits let it fly. There's a reason I enjoyed EVE online for what it was, where the systems of small gang combat got very complex very quickly, it made damage challenging and even more so if a player in your target gang made it their job to deny damage through ecm or logi. A more modern example is FFXIV, where race doesn't mater and when you get to max level you just setup a hard timed macro of your rotation, stand in a safe spot and go make lunch mid raid. There are tons of reasons why more players play FFXIV today than play EVE, simplified, in FFXIV you don't need to run through missile trajectory interactions against a target at speed in your head. On the other side of the coin, in EVE your character's appearance has no real effort or weight. In FFXIV appearance is everything to the point where there are in game fashion (Glamour) systems and a real money item to reroll your toon's race/gender/appearance. Phantasy Star Universe is a product of its time, some of the systems and mechanics have definitely been improved by systems in PSO2 and more recent titles by other studios. My concern is that PSO2 also simplified a lot of systems from PSO and PSU. Because of what I enjoy, because of the complexities it creates, and because of the creativity it can inspire, I am not at all in favor of removing racial base stat differences.
With my viewpoint out of the way, lets actually get started. There are two mechanically complex concepts that you bring up in the seed post; having techs require accuracy, or a system where techs have a failure state on hit, and non-elemental or neutral techs. Giving techs accuracy would require the entire damage stack for techs to be reworked. Weapons would need to be rebalanced to accommodate for lost damage, attack speeds would need to be reconsidered, monster hitpoints and elemental weaknesses would need to be reevaluated, technic PP costs per tier would need to be adjusted, player damage modifiers would need to be scaled. This would most likely add months of downtime or just have FO classes unusable for an extended period after Clementine's launch. To further complicate things, since damage can fail, there would be max hit creep as well which would put Beasts and Casts farther behind in max hit and damage per minute. This would also cripple tech casting for Humans as they have worse accuracy than Casts and Neumans and with this +900TP line shield in play, humans would be outclassed by Casts who would now be preferred picks for FO/HU/RA classes. It would be impossible to maintain multiple simultaneous approaches to how techs work so keeping this accuracy option as an option only to the line shield would not be maintainable in the long run without increasing the balancing workload by a quarter just to maintain a line shield. This means their patreon needs to triple or the accuracy systemic change would have to affect all or nothing. In this case it would be best if this never happened. You gain semi-viable damage techer beasts, gain Cast supremacy in FO roles, lose human viability in FO and AT roles. Imagine if a last second Resta "missed."
Your second mechanical suggestion is much simpler but offers its own complications. Techs are inherently elemental, they do a portion of their damage as that element and that portion is calculated as the elemental effect. Right now if you have a 0% elem rod, there is no modifier on the elemental % of that tech, you just get the base %. if you have 2 or more techs of the same element on a wand or rod the elemental bonus of the weapon is additive (Someone with source access please verify this for me please.). This gives you Base + Weapon mod for the elemental effect. This can be manipulated already against resisting targets by dropping the weapons % to 0. Removing the elemental base % from a tech could lead to very interesting mechanics in the long run and I would like to challenge anyone reading this to come up with a Yetch, RaYetch, GiYetch, and NosYetch non-elemental techs that gain whatever element their weapon is or run as neutral without weapon element. The other option for neutral techs is if you setup negative elemental mods off of weapons. For example if you have Zonde, RaZonde, Gizonde, and Diga on a rod, should that rod gain a Lightning elemental bonus? Should that elemental bonus overwrite the base elemental bonus of Diga to make it lightning aspect? Hopefully you can see the problems with this approach. If these weapon elemental %s were to overwrite existing tech base %s you would have people running NosDiga as any element that they need. Unfortunately I see the best option is creating new neutral techs that simply gain whatever element % their weapon gives them rather than reworking how elemental weapons work. I'm also assuming that adding new stuff is easier than breaking all the stuff we already have. That being said, making new techs from scratch is no small feat and having them interact in the current systems would be harder still.
You keep mentioning setting up new "unique" playstyles for Beast and Cast players. The sapper method from my first post works better than it would seem. Lets take a look at what else is available. For WT your tech cap is at 30 meaning you don't get the best, you don't get the worst. Its a very tanky class, so think of it less as "I'm the tank!" and think of it more as "I am the anchor that keeps my team in mission." You can focus heavily on freezes, stuns, and paralyzing to quickly lock a room down and get your team back up. DamBarta, SuZonde, SuBarta are already in the game and let you do this. To a lesser extent, NosDiga as well with the stun procs. You can run a debuffing or freezing whip in your main hand and heal in your off to help your team keep the pressure on without having to duck for items. You also have access to plenty of heavy weapons to help said team crush through whats in front of you. The class as I have described it here will not be a favorite amongst damage players but if you are running with a tight knit group this would allow your team to push through harder content without breaking the bank.
My recommendation for Masterforce will get me plenty of hate, I accept this. Procing Fire and Virus status effects deal a percentage of the targets hp per tick. If you decide to go with MF as a beast it may be in your better interest to focus on boss-killing techs as well as spreading damage overtime effects to everything you can reach. This style of play comes no where close to the raw damage output of a hard tech slinging Neuman, to be fair, not much does. Which leads me to my recommendation, a head unit that cuts TP by 130 but causes status effects to proc twice as often. Unfortunately, I'm afraid such an item may be impossible to create without introducing a lot of extra problems with the live build of the game but it would offer a great deal of options for DoT builds and an even weirder array of kite builds. The drawbacks for the item are not just in the TP cut either, freezes and stuns would end up breaking in half the time which removes a lot of control options from the build. If you were to add this item to most of the boosted status effect chance items in the game, it would work outside of the FO classes as well.
And there you have it, two recommendations, some playstyles that will have the try-hards down my throat, and hopefully an understanding as to why I don't entirely agree with your points. Have yourself a wonderful day, stay safe.