I think it is the
best solution and some developers are doing this (or similar things) already.
For example, "The Singer" developer does not release his game to the public till he gets his 'goal' (a certain number of paid subscribers on Patreon, etc) - because currently many people subscibe to get the 'paid' game and then unsubscribe till the next version is released. I believe this is due to many game fans trying to support many developers, but they have limited funds and have to make hard decisions 'who will they support this month'. Ultimately there are too many good games tooday, which is really different from 2019/2020.
I think this might be a reasonable approach here too (if
Nenad A. wants to try this model - to have a specific and steady (more or less) income, considering that he releases a new update every three monts or so (which is similar to the developer that I just mentioned).
And a 'current' version is paid and the older ones are free is one of the best solutions too, because
Nenad A. would have many game fans (especially new fans, who just found this game) and after a few free updates they might decide that they really like this game and want to contribute to help the developer.
The only thing left for
Nenad A. is to add more sexy scenes with
Jade and
Freya in each update (and more hotties for Drake obviously).