The thread Tony linked to there will point out what you'll need to boost it using stock XR2 parts. If you want to piece together your own kit that would work too but there's not much out there, and the shortcomings of the NA drivetrain are listed there as well.
A Zetec swap would be pretty cool it shouldn't be too hard to cram in there. They used a similar transmission to the XR2 so you should be able to come up with some sort of hybrid axles.
Honda? The engine would end up on the wrong side of the engine bay
Personally I would not get behind such a swap, but hey to each their own!
You want a potent, relatively easy swap? Grab an NA BP from an escort GT or Protege. It'll bolt to your stock transmission, but more ideally swap to the matching trans it came with. Easiest would be using an XR2 transmission, though - less motor mount work.
And by the way, Welcome to TeamCapri!