Default windows phone 8.1 for htc mini

Since windows phone 8.1 is now aviable for the m8 I just wanted to ask how hard it would be to get a m8 based rom for the m4?
I have absolutly no experience with windows phone and doubt it would be better than android. It would still be nice to try it out on our phone!
Could anyone with a bit port history inform me how likely it would be to base a rom from the m8?

thanks in advance!