The size and engine requirements were on thing, but I was also thinking in material availability. Such that it could be manufactured by the Finns and not just purchased. (many planes the Finns used would not have been practcal for them to build, like the all-metal Curtiss Hawk 75, and Brewster B-239)
I forgot the G.I used mixed construction (though there was still a fair amount of aluminum, but much less than, say, The Blenheim), which makes it more practical than I was thinking.
The multirole capabilities would be good too, useful as an interceptor and light bomber bomber. (and possibly dive-bomber) It wouldn't be a great dogfighter, but as I recal it was still fairly maneuverable for its size.