The ensemble picker is already sooo much faster than the previous method of adding instruments to the score, but I thought perhaps one minor adjustment could be to specify that a selection of instruments is to be held by one player by enclosing them in brackets. And this may be out of the scope of the ensemble builder, but similar to specifying aliases in the jump bar, you could write “=playername” to give the player a name.
e.g.
[fl, cl, a sax]=Reed 1, [fl, cl, t sax, bass clarinet]=Reed 2
would create
Reed 1 (Flute 1, Clarinet in Bb 1, Alto Saxophone)
Reed 2 (Flute 2, Clarinet in Bb 2, Tenor Saxophone, Bass Clarinet)
(although in situations like this it would be great to be able to disable the automatic numbering of instruments)