If you're using a weldless fitting, then sticking a butterfly valve on there would serve little benefit. As far as I know they don't sell butterfly valves with NPT threads for that very reason. You would have to go weldless to triclover, triclover to butterfly valve, then to triclover hose fitting.
If you do a CIP with recirculating PBW after you brew, opening ball valves half-way (and opening and closing them several times) will get them clean, no need for disassembly.
There are also sanitary fully encapsulated ball valves that prevent trapping liquid behind the ball.