Holistic God, a few comments on your points:
1) A total ban on conquering Cantonese, Han, Manchurian, Korean and Japanese provinces? Have pity, at least allow Russia to make the Amur river the boundary, should she so desire. (Currently 3 Manchu provinces north of the Amur, and the Chinese often colonise a few as well)
2) No conversion in India.... I'm not sure where I stand on this one - it is almost guaranteed to ensure that nobody will even
try their hands at some Indian conquest - which may be your intention, of course

And the OE should be allowed to go to India, should it so desire, in which case it should certainly be allowed to convert.
3) An interesting idea on colonial wars, but your rules seem to me to be too many to be practical, and not easy to remember in case of hostilities. In other words, it is too cumbersome for practical use.
I want a codex of rules that is easily remembered - less chance of mistakes that way, and much, much, less trouble when trying to explain to a substitute a full page's worth of information concerning colonial wars.
4) I much prefer keeping the 3 province rule for full provinces for the duration of the game.
5) On the other hand, raising the number of colonies possible taken might work.
6) Ditto. Spain must choose A
7) OE: High income, homogenous population, high manpower, good leaders the first half of the game - make them muslim techgroup in 1615.
8) Much easier to say than do. The few times I committed stupid moves in Machiavelli I for the sake of roleplaying, I felt like a terrible sucker.
9) Random leaders.
No. We do not have a tested setup with reasonable statistical distributions based on dp-settings, countrysize, and luck, that people have agreed to.
Finish such a tool, have it available for inspection and discussion, and it might be used in a later game - introducing it four days before game start is a no-go.