Interesting thought.  Myself, I switch the plane, there are plenty of great rides that have an ENY of 20 or above (190's, Yak9, La5, P47 :-) <- my personal favorite... I'm biased though...).  I think an interesting twist to the game would be to add some more perks to lower ENY planes.  I know this has been discussed for YEARS, but the flavor of the game has largely stayed the same since I started playing a few years ago.  I say let's make the maps a little closer range and encourage earlier war planesets.  I guess this will be alleviated once ToD comes on line, if ever, but I hope to see more intense early planeset battles.  Maybe that could be a solution to limiting the ENY of lower planes.  Oh well, rant mode off...