The FB is the essential cog in the flexbone.
We had a flex coach in HS and ended up running the wishbone because we had so many pure RB on the team. Had a slow Qb too, with not much of an arm or throwing ability. Teams still made the QB run by sagging the lanes we'd run the halfbacks most against the particular fronts we were playing.
Had two thousand yard halfbacks though. We still lost a lot of close games. Teams would tighten up on those players like it was a belly series to the front side and the signal caller's faults played in to greater levels. We left lots of points on the field.
What I've seen from flexbone that we stopped- get the Mike to the Mesh fast(keys FB), kill the jet/rocket on contain. Gap control. People abandoned the jet sweep vs. us(entire league).
If you force the decision off the mesh and enough people can see that and run to it, you should be all right. We usually got a LB to the handoff. If they motioned we'd basically step down with it to reduce the backside and free that LB to come over hard on a mesh key in A, the Qb would end up spilling right into contain. We knew the front side could force a cutback because the will would fill.
Everyone had a gap on it, we wanted to decrease field size to the front by contain, to the back by reduction on certain keys. We had more trouble when teams stayed set and ran to a side, but the speed off our edge would often catch the play if they didn't block both ends, so we eliminated one of the wing runners by that method as well.
From there it was a matter of physical space, unless teams gapped a mile wide there was nowhere to go, and by the time they found space between the line gaps, will would fill. Force the cutback, this year we probably don't have as much talent in our front seven and probably have to go with eight man fronts.
It might be time to develop a 46 set.
If you don't like it in the flex, go with other items. There may be other reasons to stay though, and there might be things you can develop off the flex.
I'd consider using one of the flex backs as a sniffer. You'd basically be using single wing stuff to one side and still be able to do some traps and pulls with the sniffer combo. People like the Qb to press the LOS on the series, well that extra blocker helps.
Now you can hide the ball, overload, spin counter, or even use a flood series. Simply add a tag to the series and develop new looks with what it is they want to try. You'll have a ton of options going sniffer tag to the wing side or away.
Now add the route tags others list off motion and choice to the one wr side.
Suddenly your option game has more options.
This may enable you to use things from the systems you like most, one tag and position change can do that.