Hey cool-toxic, I don't know what's your take on dividing Japan into daimyo clans, but personally I strongly support this as it allows for an interesting game with Japan, which is currently not possible with the amount of random stability drops and revolts.
I have therefore, mostly for personal use, altered the 1492 scenario to include the relevant clans, although currently it is not completely historical correct (the Hojo and the Oda weren't relevant in 1492).
I made shields and small shields for all clans (flags still missing) and did research monarchs and leaders for most clans (Chosokabe and Date monarchs missing). Shields mostly feature the uma-jirushi, i.e. the large banners that were used to distinguish friend and foe in battle, and small shields use the mon (crests) of the clans in black and white. Initially, all daimyo clans are vassals of the Ashikaga clan. Once one vassalage is broken or one clan is conquered, all other vassalages are broken too and the strive for power begins. Once one clan has conquered or vassalized all other clans, the nation of Japan can be formed and play goes on from there as usual.
Also, if you are willing to add any more provinces to Japan, I could tell you where exactly those should go to. I think the maximum amount of additional provinces should be five, with three being a good choice. I could then also create more clans.
Furthermore, if you ever plan to create a scenario in the 17th century, I could completely set up East Asia myself. I am familiar with both scenario modding and East Asian history.
In case you're interested, I have also completely remodeled the randomevents.txt in regards to event triggers and effects. Most events have additional options, revolts will be much more likely for unstable countries, and randomness in general is much more relevant for minors than majors. For example, the "Enthusiasm for the Navy" event now gives, in concordance with the description, only transport ships, with the additional option to pay a small sum to equip them as warships. Furthermore, it gives the same number of ships for any country of any size - reflecting that for small countries something like this was very fortunate, while for continent-spanning superpowers it was rather unimportant (while still nice).
I am also reworking the colorscales to make the game more appealing to the eye, see the above screenshot. In general, colours geht brighter, but not too saturated.
And lastly, I have reworked parts of East Asia in the 1492 scenario, and some other things as well, I think... If you feel you can make use of any of my work, just let me know and I'll send you the files you're interested in.