My recurring take on this recurring topic is that

1) because music making is modular and involves the ability to use many tools, it doesn't matter anymore if one tool can do everything, as long as a tool to do that exists

2) what DOES matter is that your tool brings something unique to the equation that isn't available elsewhere, so everybody has an incentive to buy your tool even if they already own many other similar tools.

3) If PGMusic were trying to be all things to all musicians, they wouldn't take such pains to integrate 3rd party solutions, like Amplitube, SampleTank and the drag & drop feature that makes it convenient to move a project to the DAW of your choice. To me that looks like they are specifically focusing on proprietary development rather than on re-inventing features that are already abundantly available in other products.

Robh, you mentioned several other software packages that you already own and which already do what you want. The tools exist for your workflow to look like this:

a) generate song in BIAB
b) move song to RB to add additional real tracks, trim sections so instruments flow in and out of the mix etc
c) export to other DAW in order to use the mixing tools that you prefer

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0