Good stuff! FS can also do this with a slight walk forward (or back, haven't played him in a while I can't remember) J3 without the airdash in the same situation. Depending on where you position yourself before your jump will decide whether you cross up or not and J3 launches without meter.
Is there any practical ways to set this up without a BGB? Seeing as you need to end in MT to do this means you can't start with a usual bnb. You could maybe start with MbBlast but getting a B3 off that is pretty inconsistent and even if you did it would cost two bars.
This is a great concept though, very nice find