The SM.79 has a role in scenarios, for sure... However, it wasn't really multipurpose (unless you count bomber/torp bomber?), and it carried about as much as the Ki67, only much slower than any other bomber in this game, and with less defensive capabilities.
Frankly, it would be slaughtered even in scenarios
That, and either the G.50 or the C.200 (either) would really round out the IT planeset nicely, though.
EDIT: Let me put it this way: Would you vote for the SM.79 if the P-39 was another option?
What if the P-39 gets done, but the B-25 is in the vote list?
What if the P-39 and the B-25 and the Brewster, and the 410, and the G.55, and the Pe2, and the Ki44 all get done, one after another, and the vote is down to He111 or SM.79?
Nobody's ever going to vote for the SM.79, frankly.