There’s several vehicles that underwent either significant change or are an original design. Not to mention, all the combat modules are original and marks Ukraine as one of the first nations to use unmanned turrets which is a pretty significant change.
Ukraine developed 2 sets of improved ERA that’s superior to Kontact-5, cornerstone of engine development, developed several of its own missile systems, etc. They also have there own hard-kill APS which is in Turkish use.
The iconic BM Oplot, Oplot zr. 2000, T-64BM, T-84-120 ‘Yatagan’, T-72-120, BTR-4, BMPT Strazh, Otaman-3, etc. are all pretty majorly different vehicles.
I mean a T-series with a bustle autoloader derived from a Leclerc design that fires 120mm rounds is quite unique if you ask me. That’s just one of several.
Also known as the T-55AGM to Ukraine, this unique modernization of the T-55A by Ukraine and with specified modifications for Peru features a 125mm KBM-1M smoothbore gun, coaxial KT-7.62mm machine gun, KT-12.7mm anti-aircraft machine gun, Nozh ERA along with Deflek-T Composite Armor, and more. The Gunner uses the Buran Katherine-E 2nd-generation thermal imager, enhanced Fire Control System with the ability to fire the Kombat GL-ATGM, the Linkey-SPZ Laser Warning System, and a 1,050hp 5TDMFA Diesel Engine. One other major change is the usage of a turret-bustle autoloader, increasing overall crew survivability in the event of a successful hull penetration.
This modernization has also been offered and completed on the T-62 which is known as the T-62AG or T-62AGM depending on the type of kit and what is equipped from it. This kit could even include either a 120mm KBM-2, or 125mm KBA-3/KBM-1M.
If an eastern/central European tree comes into being, maybe the Ukrainian M1A1 SA-ukr and Leopard 2a4V could be foldered with the polish Abrams and Leopard 2PL?
Also this is a huge long shot, but if you think it could fit, maybe the Baltic states could be included?
They may not be many vehicles, but they do give quite a few low tier ground, air and coastal options (plus the Latvian scimitars are apparently equipped with spikes, though I haven’t seen any images).
Yeah I will add the Baltics though (I planned on adding them, just forgot to update my list earlier), the likelihood of seeing the Vilkas in any type of research tree is non-existent due to it being an event vehicle.