I believe we need a way to "upgrade" an edition of a game we have already bought. For example I own the gold edition of Ghost Recon, and have noticed an ultimate edition now on there. I didnt see this before, so not sure if I'm just blind of if it has been recently added, but it would be nice if we had a way to purchase an "upgrade" for the games, for the correct proportional cost. I have seen these offers available on PSN, XBL and others, so I think Stadia would benefit. I dont fancy spending £99.99 to buy an ultimate edition while already having spent about £70 on the gold (cant actually remember exactly how much it was!).
I don't see a problem with allowing people to upgrade tiers but at the same time you should've looked a little harder at what versions of the game you can buy.
The Stadia library isn't massive and they don't hide the different versions. Use a little more caution next time.
I'm *pretty sure* I bought the biggest tier version of the game there was at the time, i did look carefully and I always do, the post wasnt about my own personal annoyances but simple suggestion of what would be a better feature for the store. I have done the same with other games too, looked to buy the big packages outright especially if they come with season passes etc.
What I'm saying is that it often happens that other, fuller "packages" of games are often released after people have bought a particular one, and having the option to upgrade would be nice.