If it is just to get into a 262 or B29 several times a month, HTC could limit the frequency any single customer account can make that transaction weekly or by tour. The problem is if someone else actually owns the credit card and the player is being helped out or underage.
Or,
HTC can give you a popup menu at the start of every tour with your first entry into the MA where you choose one free 262, 163, single B29, Tiger2 perk amount. The rest is up to you if you fly a 262 or a bunch of Tempests and F4u4 and C-hogs, or ever get in a B-29, let alone a Tiger2. This seems more in the spirit of our game style.
Hitech has always been very good at saying "NO" when the forum hoard whines that they deserve more, then run commando around the forum for a week screaming Hitech is a big meenieee.