Actually we, and by "we" I mean Chain, did it first (and better, yayy!).
We did the same thing with ErrorTrap (currently v100) for the same reason. I don't think XCAS 1.67 and XCAS 1.69 are different in any other respect. If you are on Patch 1.67, you should use the "older" 1.67 version so as to avoid the core version mismatch warning that will appear on every startup. That was years ago but I recall it was fun to figure out and fix! This happened to me when I felt sure that I had both set to the same number but turned out that I didn't and I temporarily lost all (not just custom) slider control and settings every time I took a sim into CAS. In my experience and that of other players, it's fine to have both as long as they are both set to exactly the same number of allowable sliders otherwise they battle it out over startup (okay, actually it becomes a tossup as to which one's number of slider limit gets loaded last) and players might find that none of their sliders work at all.
XCAS does so by an optional tuning file to be added in, MC by an option menu setting. Not asked about, but XCAS will conflict with MC Integration in the sense that they both try to increase the allowable number of sliders limit. For whatever reason I can't really remember right now, I use XCAS Full instead, probably because I wanted the XCAS framework for other things and was already fully "invested" in it.
#Sims 3 slider hack 1.67 mod
There isn't any point in having both and having both won't work at all, one is a core mod solution, the other is a script mod solution, for exactly the same thing.
I've never used XCAS Basic but as I understand it, it's only XCAS Full that conflicts with MC Tattoo. The skin tone mod should not conflict with anything. Although it sounds like it's all the same thing, these are actually several very different questions.