Skin bones and constraints are really powerful. Lots of things you can do! From the little I know of your setup, it sounds like it would be a good fit. 3.8 is almost out of beta, it should not be an issue to switch to it while it's still officially beta.
Aye, see the issue comments for some complexities about skeleton attachments. Eg, loading at runtime requires some juggling to wire things up, as a separate project or skeleton within a project editing animations on the skeleton unattached would be suboptimal, editing them together becomes tricky because now you have coordinate systems of nested skeletons, etc. It's not impossible, but skin bones and constraints solves a good deal of the same use cases that skeleton attachments would solve, and does so more elegantly.