HI Gra
Recoil and BB are not the easiest of bedfellows. So on board - no. But I seem to say it over and over again - You can add recoil to anything just by using your 9X. So if you did come up with a recoiling BB gun just use the 9X to program a recoil servo.
For everything else there is Sirvoe.
Specs is easy as far as Taipan goes - Everything

But costings on T2015 will scare you so there may actually be 2 cut back boards, Asp & Diamondback
As far as Diamondback goes - I've completely reworked the board almost from the ground up thanks to a suggestion by Andrew. (reduced costs

) So the prototype above is already in the bin

Asp is for the smaller Panzers as T2015 and Diamondback are a bit on the big side.
Specs are not final as I am still finding I can add extra things without pushing up costs.
Asp the smallest of the 3 will probably be available first
Cheers
KG