Several comments here recently about people buying the latest Xtra Styles but not having the required RealTracks to use them. Here is a solution.

For every style, program a backup default RealTrack that is included in every BIAB since RTs were invented.

So, if new Xtra Style "2021 Country Gold" requires a drum RT that was only included in Biab 2021 Ultraman upgrade, automatically select an older mostly compatible RT that the customer does have.

Or, when the new Xtra Style is loaded check for missing RTs and have a wizard that guides the customer through selecting their desired replacement RT.

Good observation. I like the second proposed option better, because with the first (automatic substitution), they would not know what they are missing.

Here is the PG Music solution for folks that need a RealTrack from a package they don't have.

It's in two parts.

First: The UserTrack Wishlist Forum where a user that wants to make use of a particular style from the Xtra Pak 11 Style Pak not owned, that user can make a request in the User Tracks Wishlist for another user that does own the Xtra Pak 11 Style Pak to receive an SGU file by email, apply the appropriate style with the proper instruments, then email that SGU file back to the original user with everything necessary for that Xtra Pak 11 style to work with that SGU file.

Second: The email share SGU file feature.

Both have been around since at least 2013. Note that the email feature will identify every type of BIAB file necessary for the SGU file.
There is also no special requirements or restrictions to sharing files between the different OS, or version of BIAB the users own that I'm aware of.

Interesting work-around but not very practical in my opinion. It is late on a Saturday night and I decide to use a style from my Xtra Pak 11 but then I find several instruments are missing since I don't own those RTs. And your solution is...go to the forum and hope someone who does have the missing RTs will download my SGU, load it and apply the proper style with RTs and then send it back to me? First, my workflow is gonna be interuppted by hours or even days if I even find someone willing to help out. Second, I don't think the RTs will be included in the saved file so I won't be able to change anything, not even a single chord or add a single bar in my song. Finally, the odds of two forum users (me and someone else) remembering this obscure technique when it is needed are not good! Also, I fail to see how this is related to UserTracks???

So, with all due respect, a much better solution is for the software to handle this or for PGM to simply not sell expansions to people who do not own the prerequisite for using said expansion.

Even during the automatic substitution it should flag what was missing and what was used to replace it. Perhaps along with an offer to purchase what was missing?

Yes, that sounds good.