We definitely know that the 18+ aspect is a major draw for the game, we’re not ignoring that, we will continue to provide ways to get the NFSW version where possible.
The plan we have is already basically what you suggested, make the itch.io page free leaving the demo as is for now, and use the page to promote the Patreon. The future updated demo version will also include the 18+ content on itch but again will promote other platforms to get the full version.
The change to SFW is a minor one, only replacing the explicit relationship scenes with non-explicit suggestive lewd scenes(M rating vs AO rating)and would allow us to be on other platforms besides just Patreon.
Both Steam and GOG allow SFW games with 18+ patches, which is a common practice on those platforms, and so we’d provide the patches like many other games do.
The SFW version would also allow us to get on platforms that can’t/won’t/don’t allow this type of graphic explicit content(whether that be payment processors, or other reasons) but do allow strong sexual themes, like the Epic Games and console stores.
The only reason the game would ever become 100% SFW, is if there were a “porn ban” a.k.a. A law that made it illegal to produce/distribute 18+ content in the US.