Jeff, I've played with and have seen other transitions similar to this one. Other than the obvious which the others have pointed out (the bicep slicer, omaplata and triangle, if your post arm slips) there are a few other things to consider.
1) When your releasing your post arm on his thigh to go to the "shot gun" grip on his leg you are giving your opponent a window of opportunity to recover his position to be able to go back to the above mentioned attacks. The tighter your transition the increase in your percentage of success. Also the "shotgun" grip is powerful, but make sure you don't "dangle" your hand on the outside of his leg, your elbow and armpit hanging over are fine, there is a quick omaplata/kimura variation that'll ruin your day if you don't. I don't see it as a threat from this particular transition. Its just a good habit to get into as its pretty easy to hit from you basic knee bar positions.
2) My personal experience with knee bars is to attack the leg where its at. Movement begets more movement, the greater the distance you travel to the leg, or the more you move his leg/hips, the greater the opportunity for them to escape. You'll have to be very careful once your partners catch on to the roll up escape i.e. they roll up on top due to momentum you created by pulling their leg across their body allowing them top obtain top position, crossfacing, sprawling out then circling to side control.
3) Watch your left foot, its a hail mary but you are leaving it open for a toe hold, if they can secure it before you finish your transition, your going to find yourself in a scramble rather than catching them in the kneebar.
The great thing about leglocks is the surprise factor and that most non-elite competitors have a very limited knowledge and understanding of the positions and transitions for successful legs attacks and counters. Unless your opponents train them on the regular you'll have a distinct advantage when attacking the legs. So even with all the critiques of this particular transition I'd say move forward with it, clean it up, have your training partners start attempting to counter it, show them how your setting it up, and let them know what their potential counters can be. The better their defense the tighter your offense will have to become, which will then open doors to other attacking combinations.