+10% resistances from all sources
can exchange 20% of charge for airblast (mouse3 or your bind to activate)
50% slower shield meter charge
when you stop charging you retain the charge left in the charge bar(secondary fire ends charge without swinging weapon. if you swing you still lose the charge)
-50% knockback

i think since its an "airlock" it should be able to airblast, also it would give a demoknight a more "team" focused outlook i.e. putting out allies or reflecting projectiles while still making it not spammable
also, the 50% slower charge refill will counteract the persian persuaders ability to make this an airblasting machine