Now that I don't know the answers to as I never adjusted the price for an existing DLC pack. You'll want to ask N3V that for an official answer but my guess would be it'll remain the same pricing but again, ask N3V about this.
With how it works, at least from my understanding, if version 1 works for TRS19 and version 2 also work for TRS19 then no version 1 won't be available. I had a few DLC updates that were made in S5 and SP4 users also to the SP5 update. The only exceptions to this is if the DLC was made back when TRS19 was originally release with the DLC downloader or if version 2 was made in TRS22 then version 1 would remain available to all TRS19 users.
As for sales while just doing something like volume 1, volume 2, etc N3V said it won't work out well since they'll have to manually issue discounts for users that purchased one of the versions. I had this idea for Centrall Sub since I have a session pack I wanted to package up but can into the same problem as you - TCCP doesn't support session packs outside of the KSC route.
So what I would suggest if you want both versions? I would just do the upgrade to an existing version and make version 2 for TRS22 and newer. This way version 1 remains available and those that want version 2 can use TRS22. Just my 2 cents on this.
Cheers