As ever I'm on the wrong platform to try this, but this looks like it may be worth experimentation...
From the manual page 112, near the bottom:
Type a chord with a break followed by a number (N), and this will copy the break for the next N bars.
e.g. C7...4 will enter held chords for 4 bars.
Gm7...bd5 will enter held chords (bd=except bass and drums) for 5 bars
The usual function of BIAB is to end the hold when the next chord symbol appears, which is what's breaking your attempt. Hopefully what's shown above will honour the x-bars even with another chord.
Another possibility might be to mute or otherwise turn off the drum track in the first bar, but mute (e.g., via F5) can be a bit brutal.