Hello, everyone, long time reader, first time poster.

I recently got a Sinclair PC200, a marvelous little XT-in-a-keyboard that I wanted to get specifically because a) I wanted an XT clone, b) I have a thing for keyboard-computers (like the C64, C128, Amigas, Atari STFs etc.).
While it's upgradable as-is (I know I can fit a NEC V30, an 8087, 640 kB of RAM and a Gotek if need be) it only has two slim-profile 8-bit XT/ISA slots.
This makes upgrading it further tricky - I don't think there was ever an ISA sidecar for it, I'm not sure if the floppy drive/expansion cart can be used for that.
There's the additional issue of the "sunroof" - I can, in theory, fit a full-width card inside, but then I have to keep the "sunroof" open which could draw dust and invite general FOD.

So here's my practical question - is there a way to produce an XT card that could, for example, combine the capabilities of two standard ISA cards into one? For example, so I would have a single board with both an XT-USB adapter and a (say) AdLib clone? I'm not that familiar with how the ISA bus is laid out on XTs (this is my first machine of this type) and how it's shared, but if the boards could be condensed into one, it could give me a lot more flexibility.