And the most obvious, to my mind, set of variants isn't even mentioned. It's a fact that the German DB605-powered Spitfire used the BF110 cowling because the contours at the firewall were very close. Why not, then, transplant a pair of Spitfire engine and cowling installations on to a Bf110. Exact mark of Spitfire used would depend on when the conversion was done, as well as in whose service it was done. I could see Spanish-built Bf110 variants with either late-model Merlins or Griffons; for a bit more outre variation, Griffons with contra-props.