Maybe go to do it early, then by the time you've switched the looper you'll be on time ?
A lot of looper guys like Steve Lawson and Michael Manring, and myself when I was doing a lot last year, don't do what you're trying to achieve. If they use 'percussive effects', then they create them themselves using their bass, so it's part of the loop, not outside of it.
Some loopers can be connected using midi to drum machines, particularly the Boss ones.