Alright... this is what I'm thinking while sippin':
This is the new "Settings" page (two images due to vertical scroll required now):
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My gut is telling me to scrap the VN's Text outline, transparency, and size... as well as that "Line Spacing Scaling" option (that one is a RenPy basic for accessibility that can make things really wonky). Doing this I can simply use the existing mod Core's outline, transparency, and sizing like folks are accustomed to.
That would leave use with the dialogue text color which I should be able to keep without too little drama... that way you have something new to play with. What's odd is that he coded the dialogue text for the straight-up talking dialogue but the "thinking" dialogue text is all still jet black... no option there. I'll insure it has white outlines so readability won't be an issue.
Any thoughts or suggestions are welcome as it'll take me a bit to carve out some code mixing both the VN attributes and the Core's.
P.S. - yes, if the dev was stable (not changing RenPy versions all the time and changing base code) and I adored the UI enough I'd spend the time to allow you to select either the VN's settings or the mod's and make it toggled which to use but that's all a shit-ton of more work and I'm not sure I wanna walk down that road right now... maybe later.