This would definitely be neat from the point of skill required to do it.

A few challenges that come to mind are:

1)  Miata is a unibody design, with no real frame to speak of.
2)  Assuming you can place a Miata body/frame onto another frame, I'm not sure what you would use, being that the Miata is such a short wheelbase, possibly a Sammy frame.
3)  The location of the existing wheel wells vs the driver position will produce an awfully short rear driveshaft.  Note that the transmission shifter on the miata is literally placed so far back on the transmission that is is dead even with the end of the transmission output shaft.

Anyway, that's just a couple of thoughts.