Sorry, but no, not really.
First, the average number of perks/h I gave includes already a quite high percentage of higher ENY fighters being flown. It's not that everybody or even the majority is flying the P-51 all the time. The 'average' ENY fighter's flown is much higher than 5, more like 12-15 (would have to check the current status), and this is how the 2-3 perks are created. If a individual player would actually fly only D-Ponies, the number would be even lower!
The bold faced text is the point I was getting at. An individual that cares about perks should fly an average or higher ENY planes. Of course, if many players care about perks and take my advice it will just raise the mean ENY. Also, I suspect (just a hunch) that there is a difference between the mean and median ENY - if 9 players fly an ENY 5 planes and just one flies ENY 40 plane, the mean ENY is 8.5. Just 1 out of 10 players has had a significant relative impact on the mean ENY (50% increase of the mean).
This is why I suspect that the mean may be 12-15, but the likelyhood of meeting ENY<12 plane are higher then 50%.
Second, there is a limit the average player can do with very high ENY planes. While it's true that flying an ENY 30 plane will get 3 times as much perks for a single kill than flying an ENY 10 plane and indeed not getting home to land them only cuts your earnings down by 20%, it may be even more harder to get any kills in the first place. For the average player, this can more than offset the increased rate of perks being earned. Concentration on killing ENY 5 planes in high ENY rides sounds easy, for the great majority of players it is absolutely not.
There are quite a number of very capable ENY 30 planes. Are they inferior to the ENY<10 planes? definitely, and this inferiority will be strongly felt if used for dueling. However, in MA furball environment, the impact on your kills/h will not drop it to 1/3 of what they can kill in ENY<10 planes. I dont want to name specific planes, because I don't remember the specific ENY values of most, but last I checked there were VERY good high ENY fighters out there. Just in relative ENY terms, I am sure that going changing La7/La5, or Spit16/Spit9, or P51D/P51B, or P47N/P47D11 or 190D/190A8 any player will get a significant boost in their perk gains over whatever they gain right now - including some reduction to their K/D.
This will be even more effective to noobs, because they get kill of opportunity more than by out-flying their opponents. For such kills, the 190A8 kills even better than 190D (just an example) and P47D11/25 kills just as well as P47N/M.
Then again, if everyone does this, the median ENY will rise and going high ENY will be less effective in absolute perks/h farming, but still better than flying ENY 5 plane.