The Montage is just focused on totally different demands than an arranger, and I don't think it is the best choice for a typical arranger player.

With my MoXF I have spent hours at night to edit the best strings ensemble - combining up to eight different waveforms, using filters etc. - I just don't think the typical arranger player wants to do these things in a time-consuming way.
And the Montage is even much more extreme in this respect: especially the FM engine requires much more of programming and knowledge about that type of sound generation compared to a sample-based engine (AWM2).

Of course, you can just use all the presets instead of editing yourself - but then a large part of the Montage's capabilities are wasted. And furthermore, even if many acoustic sounds in the demos are impressive, I think the typical arranger player would quickly miss some typical acoustic sounds - how about Mariachi trumpets, Hackbrett, 30 types of Accordeons etc., the Montage range of sounds has a different focus.