I think this is an excellent way to encourage people to financially support the project while also keeping it open and free. However, I have a few suggestions to help make this as successful as possible.
First of all, you need to understand the Asset Store audience. You can get a great sense of this by just looking at the top selling / grossing assets on the store. These include:
- Playmaker (visual scripting)
- Realistic Effects Pack 4
- Archimatix (node-based modeling)
- UFPS : Ultimate FPS
- Gaia (easy procedural terrain generator)
- ProBuilder Advanced (level editor / modeling)
- Shader Forge (node-base shader creation)
You will notice that almost all the top assets on the store are beginner, artist, or non-programmer focused. This is an important thing to remember if you want your asset to also become popular and therefor successful. This is not to say your asset must fit into one of those categories, but it should try to appeal in some way to these non-technical demographics if you want it to have widespread success.
Another excellent strategy is to release a free asset and / or free lite version of an asset just for promotional purposes on the Asset Store. This eliminates any barriers to entry and allows you to generate lots of downloads and reviews for the asset. Which will help push the asset up the list of popular assets and make it more visible to more people in the store. This in turn will drive more users to your own store page and any other paid assets you have. You can also advertise your paid assets as upgrades inside the free ones.
At the moment I'm a little confused as to why the default version of Entitas cost money on the Asset Store if you're already planing to charge for the Plus version? I understand this might just be a way to allow existing users to support you already, but the price tag will also greatly discourage any new users from picking it up.
So in my opinion I think the default version of Entitas should be free on the Asset Store. This is also the only way to get it above page 100+ on the store and will help you promote the plus version when it's released. Now I'm really looking at this from a new user point-of-view, but I think you have to look at it that way if you want to succeed on the Asset Store since this is what the majority of people there will be.
As for the paid version(s) I would focus on learning examples for newcomers. Perhaps you could create a complete game example / tutorial that covers all possible use cases and sell that? Converting the official Unity Tanks!!! Reference Project for this purpose.
Also, if the roslyn code generator is an essential tool for helping new comers then I would greatly discourage putting it behind a paywall. Since I'd be afraid this could greatly hinder new users from embracing Entitas if they run into any issues. It's a tricky balancing act, but I would only charge money for non essential extras. You just need to make sure these extras are still very enticing so people still want to buy them. I think the free and paid Game Framework Assets are a good example of how to do this right.