Diversify aircraft, people LOVE a choice.
If your going to capture a field your going to need at least 2 types preferably 3.
A Deack town & field, cannon birds for this job.
B Cap Might consider P51's or spit 8/16's here.
C Town & VH killer, you want planes with good ord loadout, and that can follow up with mg/cannons. 110g's make awesome town killers, as do mossies, a20's, b25h's, etc. IF you have the cap to cover them.
You can Merge A & B, but you are going to need more #'s if you do. Lose half your cap deacking and your in trouble.
Saw one mission yesterday for knights had 2 plane types. 109g14's and c-47.
I did a "roflmao" on country and the mission disappeared.
If you want to do a "theme" might consider a russian one.
La5fn's for de-ack, Yaks for cap, iL2 for town killing.
But give people choices of planes in missions and you'll have more people joining.