I would personally love it if the server came with all the features, and like Express it limited hardware. I would like it even more if the increments, and buy in were a low bar allowing you to scale your environment very granularly.
A good example would be something like:
Each 1GB RAM or core/processor it will use for SQL Server would be $100, and just give me all features, like you said.
Then, also make the lowest buy in remove any restriction on DB size. Realistically, any serious business will need to scale RAM/proc with DB size unless it has low use.
So, I could buy two licenses for $200 and get all the enterprise features, but the hardware allowance would be about the same as SQL Express, so it's not like I could run an airline booking system on it.
Just my two cents,