I found a program that SORT OF does what I need except:

1. it's for MAC and LINUX with only an out-of-date port to Windows;
2. it's for drum tracks only;
3. it can only create one-measure patterns (but can handle odd time signatures);
4. it does not insert time-signature events into the exported MIDI file;
5. the data is entered via the mouse and/or computer keyboard rather than a MIDI controller (though I might be wrong about #5); and,
6. can't get it to run correctly on anything more recent than Windows XP.

There are videos on this page:
http://www.hydrogen-music.org/hcms/node/44

Check out 1.1 Tutorial 1 : pattern editor.

Pretty cool freeware program, notwithstanding 1-6.

Is there ANY WAY I can make PowerTracks do this?

Or is there another program that's better than Hydrogen (not necessarily freeware)?