Oh Steve i have so many ideas i dont think you can handle it jk. My idea so far for the Megalodon is set to appear as one boss in the first Ship battle and 2-3 in the Second. Needless to say it wont be easy
Or you could just have Darksol appear briefly in an intro during the second ship battle, and rather than have Nova talking, have Darksol summon SF2's Kraken boss, while saying RELEASE THE KRAKEN.
That way, you only have to import the Kraken sprites and attack patterns from SF2. Replace the P. Knights, shellfish, and seabats with the Kraken's legs (melee), arms (archers), and massive head that can spew bubble magic from 2 spaces away.