if the RA climb leads us up into IMC while below MSA. This was my main concern initially, regarding TA/RA while VFR.
Interesting point - never crossed my mind!
I used to fly Jetstreams and I had an RA with a Tornado in the Scottish FIR not that long after TCAS was introduced on the fleet. It was by no means the first nor would it be the last RA against Mil traffic! We were IFR but in good VMC at the time.
That example showed me that TCAS is an excellent tool when used in the open FIR when there is fast jet military traffic nearby.