Hi, I have Rollei 6008 Professional with those lenses. You anyhow can't use the real power of PQS lens with 6006, i.e. 1/1000 sek shutter speed, but it will work as PQ lens. Planar is Planar. Point. Distagon 50 f4 is a very good lens. Depending on your budget Sonar 150 f4 can be good choice. With lenses check filter thread. EL lenses use 67mm standard instead of Bay VI mount, construction is exactly the same.
It might be be reliability problems, but I think not more often than with other cameras. I do not have problems. Battery life is for me OK. Approx. 400 shots (6008) with a battery makes 30 rolls of film. If You by an insert for battery pack I'm not sure how it will work with the old charger. Big capacity replacement pack is NiMH and original battery is NiCd.