RB lenses will work on RZ bodies but NOT the other way 'round. You seem to have the hots for an RZ kit that duplicates what you have with added disadvantage that its lenses won't fit the RB--not smart. 50-65mm C RB wides aren't scarce nor are they that pricey. Provided your current RB kit functions properly, why chance a new kit that might not? Your client presumably wants results. Get an RB 50-65mm(your 90 probably isn't wide enough--assuming you've checked), finish the job, and futz with the RZ/RB conundrum later. FWIW, the KL series lenses for the RB are superb and identical to the RZ lenses, save for the electronic shutters. They aren't as cheap as C lenses but they are sharper with better coatings.