Was going to comment that most of these situations are covered better by a 'break' than having to stop then restart by hand or footswitch. Timing critical things like this are best left to the machine...
Mind you, it's good practice to see if YOUR timing is spot on...

Maybe if you can hit the one PERFECTLY every time you use a bar break (complete silence, not a break/fill), you might have good enough time to do it by foot or hand, but you'd be surprised (especially if you record it and listen back carefully) how hard it is to be that precise, especially in the heat of gigging...
I DO like the Audya's four break/fill choices, though. This is something that other manufacturers really need to jump on, as the B/F during Var1 isn't really anything that ought to work in Var4 (and vice versa). One just doesn't seem enough to cover all your needs...
Me, as the Roland's don't have a B/F (just a break), I'll hit the break switch on the one, then hit the fill switch (I do it all with my feet) on the three or four if I need a B/F, or just leave it silent for a full Break... Works pretty well, and at least I get a different fill depending on the Variation. The thing is, Breaks often need YOU to play through them, sometimes with quite a signature lick or flourish, and doing everything with your feet allows you to do these with both hands (if needed)...