No, I don't think it works that way. You might be able to install the complete ACR mod, and then leave the sofa-socials out (but why would anyone want that?), but not the other way around!
As for a sofa-woohoo hack... I believe you might look into Dizzy's work (available at Crazy Town). He's made a hack that transforms Make out on a sofa into sofa-woohoo, if I'm not mistaken.
Thanks all for your comments and the interesting follow-up discussion.
Yeah, as cool and tranformative as the ACR could possibly be, the only nice thing I like about it is the whole casual part... not so much on the autonomous part. I don't really want timers to count down the last time I woohoo'd or made out, as my neighborhood is less General Hospital (those characters sleep with everybody!) and more mixed bag.
Although the prospect of a random booty call is nice, I can always just pick up the phone and do it myself. I'd rather have the option of picking and choosing which Sims want to do it, where, etc... Maxis defaults are certainly not ideal, but I'm not quite sure ACR is either. I know that the ACR is configurable and that there is a reasonable (high-level?) amount of configurability, but I'm just not ready to make the leap... yet.
I just signed up over at Crazy Town and found
the mod in question. The mod will consider a "makeout" as a woohoo, but only if both Sims are naked, and the "get naked" mod is not included. To be honest, I'd prefer to have a new pie slice option altogether for woohoo while on the couch but using the makeout animation (and have their clothes be removed in the process.) Sometimes making out on the couch can be useful for my more prudish Sims.

Any idea how in-depth and insane it would be to try to make this mod myself, perhaps using an existing mod as a base? I'm confident it might be very complex, and I certainly don't want to break anything.