Where might one put Sonny?

I've been trying to work Sonny into my AU somehow - the AU is really just my take on a bunch of stuff while veering closer to RWS vibe-wise. I thought it'd make sense to have Sonny work on one of the various mine or quarry branches given what kind of engine he is. My initial thoughts were either the China Clay pits or the Blue Mountain Quarry.

The former has him with Bill and Ben, which would also put him along Edward's branchline and that could be fun as far as character overlap goes. The latter would mean he mostly hauls stuff out of the quarry similar to Paxton, since he's still standard gauge, but having him interact with the Skarloey Railway engines could be really fun too.

So uh. Anyone have any immediate vibe-checks on that? Suggestions, criticisms, other feedback, etc.? Other mines that I've glossed over? I've found a few different options for mines but Sodor doesn't seem to have any coal mines in the RWS (at least until later, maybe???). Obviously BMQ isn't from the RWS but it's located such that it works for this AU. I debated bringing back an older mine or something, but the various closed mines have pretty good reasons for being closed.

(I've kinda been spamming the questions lately, apologies if this isn't really the right place for this kind of question.)