If you get hit with crippling strike in melee range with your build (sniper/smg), then you have to switch to the smg already, sniper has harsh close combat penalty. That is what you have the smg for, short range bursts. And since the smg has no strength requirement, it does not matter how many crippling strikes you get hit by.
(However, if you get ambushed in melee with 3 constitution and no dodge or heavy armor... well you really want to avoid that.)
Full-Auto is not a bad idea in itself, more power to the smg is nice, but then, you really want to switch to assault rifles instead, they are more powerful. So you are leaning into another kind of build there, with the sniper as more of a backup.