Thank you, that's great to know. This definitely won't happen for a couple of months at the soonest (lots of great features to add before that).
There are, in fact, some problems with using external hardware to trigger certain events, like snap-to-default. There are several ways to handle this, such as beginning the snap-to-default event after not receiving new MIDI data for XX miliseconds. However, like most things, until we actually implement it and try it out, we won't know what's a good idea and what's not. In fact, this is why MIDI Designer has big advantages by being such a small company (though this sounds backwards, it's not, or at least in a lot of cases).
I'll comment back here to enlist your help when we're at this point. Good luck with MIDI Designer and thank you for the open dialog!