Since their introduction back in Stormblood, Ultimates have always provided genuine usefulness for completing Savage raids and farming gear outside of hitting bigger numbers in content that doesn't need it. With Yoshi P and team continually confirming that there will never be more than 2 ultimates per expansion, this will always leave one of the savage tiers without a subsequent ultimate to farm gear for. So far this has always happened in the x.4/x.5 patch cycle where gearing via savage is even more meaningless with the final step of the relic weapon. At least for me, this has made the last tier feel meaningless to grind as the gear that is normally farmed to tackle the hardest content in the game doesn’t exist for the last tier of the expansion. Even if you were to move the 2nd ultimate to the x.5 patch, the x.2/x.3 cycle will now have that void.
In my opinion, upscaling legacy ultimates to max level is the best way to resolve this problem. You do not have to do every single ultimate every x.5 patch either. 7.5 start with UCOB/UWU/TEA, and then 8.5 onward just do 1 expansion worth each time (ex: DSR/TOP for 8.5). This essentially becomes a permanent “unreal” type of content for ultimate. It will require you to have unlocked the legacy version of the ultimate, and have completed the current savage tier. The Savage gear iLvl will be the new BiS for the upscaled fights. This will also give them a reason to add weapons for the new classes that did not exist when the ultimate originally came out. This would mean UCOB/UWU would get 6 new classes added, with TEA getting 4 new classes. They could do an entire new weapon set if they wanted, but I think just adding the new classes into the mix would suffice.
The unreal version would reward the player with a new totem. This totem can purchase the new weapon unlocks released with this upscale update, OR they can be converted to the legacy totem to purchase the original weapons. This makes it so you don’t have to also clear the legacy version to get certain weapons even though you may have only cleared the new unreal version. This also opens the door to simply truncating the old versions of the fight all together if that works best.
Overall, I think this concept would fill the void of one of the odd patches not having an ultimate, add legacy ultimate weapons for new classes, and provide additional content to players that doesn’t require creating something new from the ground up.