My club does a postal 20m indoor benchrest to NSRA rules. Smaller targets I believe no time limits etc and only a flat front rest can be used - cheap and simple both rim fire and air compete together with iron sights or scopes in different classes. All marked with a .22 gauge.
It works very well - however as you say lane time will be the issue - it does stress some of the LSR guys as it uses up both of our lanes for one shooter, but 10 mins to set up 10 shots per target - all done in 20 mins really so no big issue. Compared to 10m guys setting up and shooting a couple of sessions of 60 shots - you can sit there getting old waiting for a turn!
Good luck setting up!
FTP900 +Sightron S111 10-50 x 55
AA Pro Target in FWB FP70 stock + MTC Mamba lite
Daystate Airwolf + Bushnell Elite 6500
" life is about the memories we hold and not the things that we own"