One is "free" to try to shoehorn a V6 into a Gremlin.  If you are not a mechanic, it is easy to flippantly suggest one go ahead and do that.

 

The reality is, it can't and probably shouldn't be done and, should you manage to accomplish it, will ultimately be unsatisfying and probably silly.

 

The question on the table is why did they build a Gremlin?  Edit to add:  ...And how can we stop future projects from becoming Gremlins and be more useful to a broader market?  One way is to make a car that already has a V6 under the hood.