Graham - I honestly think that's fairly flimsy reasoning given that you've virtually re-written another man's well-known song.
A mutual acquaintance of ours who has in the past claimed a familiarity with pelagic whaling was treated with icy politeness by the author of a modern whaling song he sang one time, in the author's hearing, said singer introducing the song with glaring errors and outright lies. You know who I'm referring to, no doubt?
The great man Hamish Henderson made observations on ownership, along the lines of how much of a compliment it is to a songwriter to realise his song is no longer his own, that it may perhaps becoming a 'folksong'.
This cannot possibly mean that we have license to deliberately reshape another's work to our own ends/tastes. That seems to me unethical.
If you like it, sing it and let it evolve naturally in the (folk?) process. If you don't like it, write a new one.