I'd definitely enjoy a more standardized API for testing optional feature presence.

We already have system-configuration-features, seems like it's reasonable we get system-configuration-working-features(can't think of a good name), which would do X-available-p for every X in system-configuration-features.

But first we'd have to get X-available-p(or some other convention) working for everything. Would it be acceptable for Emacs to ship with a small image in every supported format? Then imageX-available-p can be implemented by opening that image and catching the failure in create-image. I know that the spash.* image is already shipped in most formats, even in bmp for some reason.

This would let you quickly test which features are working... Now I have to go through a checklist. Then I'd be able to automate such a check, which would be pretty helpful.