Hmm, I don't think this takes into account the business model for Sex Sim.
Currently it works with you getting the very basic package for free, and add on each of the animation packs and customiser options by buying them. I think Jak's been very generous with this model, and with the amount of customisation possible, as if people are making their own content for the game they're not buying the stuff he's made.
I think with your model it would be much too easy for people to just download the free version, maybe buy the modifier addons, then make whatever they wanted for free, cutting Jak out of the loop so he earns much less for all his hard work.
Just as it is, you get to buy the things that interest you, and pay for what you're going to use, and I think it works very well, especially as it's just one guy making all this high-quality stuff! I know we all have lists of stuff we'd like to see added, but unless you want to donate a huge sum to help Jak hire people and start a proper studio, I think we'll just have to wait for him to finish new and exciting additions to the Sim in his own time!
Also, to Jak, thanks again for adopting this free-to-play-paid-addons setup for Sex Sim, it's so much more user-friendly and neat than the average premium erotica's 'give us your credit card info now have a half-baked and poorly-supported "finished" product', I hope it's working well for you running it!