Matt,
I don't believe non-integer tempos will solve this one, as it will have musical content / instructions within that bar, given current setup: stretched, pitched RTs and MIDI. What I am talking about is a no chord n/c - no sound pause, that can be controlled by entering a decimal number. For example entering 2.5 will create a 2 1/2 seconds muted blank... lets call it a bar.

In another words, it will not act as a timed "pause" as far as transport goes, everything will still play, but it would create that blank, free of instruments no-chord block.

Alternative to this request is to be able to create a No Chord bar and specify time in terms of seconds how long it should play for, regardless of the beats in it - as it will have no musical instructions to follow, except for time you enter.