I don't think that's currently possible (maybe with some java script that's running in BTT, but that would not be trivial).
I think the key sequences feature would would need (in addition to the "max pause between key presses") a "minimum pause between key preses" and additionaly a way to to match a range (or all) keys. Both could be nice additions in general, I'll check whether I can add this.
Maybe I said I would like to update them However the algorithm is already super complicated - so I'm very careful with any additions there. But these two seem feasible.