Would there be a compression problem running it sans turbo? (Hearsay has it that it would be a "dog".) 

Definitely would not be a “dog”.  Best I could figure based on data that Mazda generated, at 5500-6000 rpm the 9.0 compression could be about 4% penalty vs 9.7.  More at lower rpm.  And that would be for WOT. If you run a 2.85 : 1 re-drive ratio and run 6500 -7000 it’s likely there is not a measurable difference.