This is remotely something similar to the situation between Rus' and Ukraine. Therefore, you can think about the possibility of the revival of Rus', if the civilization controlling Kyiv has critical problems with stability. This revived Rus' can be called Ukraine with a Ukrainian leader.
The problem is that modern Ukraine is very late civ (short-lived republic of Ukraine existed in 1918-1920 iirc and as rule of thumb such states are represented as Independents, and modern Ukraine was formed in 1991, which technically makes it unplayable). Another problem is that Ukraine should appear if its core owner (naturally Muscovy/Russia) is unstable, but i have yet to see a game where Russia collapses without player intervention, and players that have goals to destroy Russia (Prussians, Ottomans to some decree) usually don't want Ukraine to appear, which puts idea of modern Ukraine as Peru for Rus' Incas in an awkward place, being totally reasonable via precedence but sore thumb from gameplay perspective.
However, it would be very reasonable to include Zaporozhie/Cossacks incarantion of Ukraine/Rus'... unless Leoreth decides to make it Independent, because Zaporozhie was regional power at best. However, the idea allows for some fun UHV goals and UUs, like moving Cossack to Rus'/Ukraine and adding Russians some modern UU like T-34.
Regarding exact
Rus' UHV - i guess everyones idea is to add famous
Varangians-Greek trade route, but the problem is that both Vikings and Byzantine tend to be extremely unstable, and simple trade connection can be solved with a few roads which is simply not satisfying even as part of the goal. Another idea is to make Rus' UP food generation from trade routes (not a good bonus, but every other possible food bonus that won't be broken flat +1

from farms is already used by Chinese, Mayans and so on), with
UHV1 being generating X food from trade routes. It should force players to settle/conquer Novgorod, a Black Sea port, and naturally connect all three cities.
UHV2 can reflect alt-history where Rus' survives Mongol Invasion as independent power. Could be something about not losing cities to Mongols... but then you probably shouldn't lose them to Polish and Russians as well, which makes it simply "don't lose cities" which is, again, simply not satisfying unless paired with something related to average X of cities to avoid cheesing through purposeful loss of cities. Average food production? Average culture (icons go brrr -
Icon Painter as
UB Theater, giving Priest and some happiness)? Average trade income (given RNGish nature of trade - probably bad idea)? Maybe something like "control X farms/buildings" to force players to have many cities and defend them all, making it less trivial to not lose them. Also, i sincerely think that adding Rus' "anti-Mongol" unit is a bad idea - Rus'
should naturally fall to Mongols and have tough time against them.
Druzhina being Lancer with Amphibious is way cooler and more useful in region filled with rivers.
Rus' also weren't above some good pillaging and raiding; Igor famously had his shield nailed to gates of Constantinople (although it might be a myth caused by blending of two separate events); Novgorod's
Druzhina pirates were as much vicious as Vikings were. Therefore, raiding/pillaging might be
UHV3, but it will directly contradict diplomatic nature of
UHV1. Another possible
UHV3 might be Novgorod/Kiev winning power struggle against Moscow, represented by controlling Russia at some point (1600 or 1750, reflecting formation of Tsardom of Russia and Zaporozhie submitting to Russia respectively), but it just repeats
UHV2. It can be rearranged as "food generation UHV, trade/pillage UHV and territorial UHV", but the trick is to make them not contradictory.
A problematic civ for sure. The only one i presume to be tougher to implement in 1.19 gonna be Kanem-Bornu (due to the fact they are both isolated and historically modernized somewhat faster than other African countries, and i personally find Africa super meh in current incarnation of mod, being bunch of isolated civs which never interact with anyone in ways other than selling stuff for UHVs).