So would it be acceptable if on the box it said Multiplayer available for a fee? I am trying to understand where the line is drawn. If a game is primarily single player, but has multiplayer available for an extra fee, how is it different than DLC? They both cost additional money to develop and if you made games I am sure you would want to be compensated for the cost of all value added features above the primary product.
I am not arguing against your idea, merely trying to understand it and maybe learn from your perspective.
It really depends on how integrated the multiplayer is to the game's experience.
Say for example, Mount and Blade. I play that exclusively single player without ever wanting/needing it or feeling that I am missing anything by skipping multiplayer. (Mind you, it does not have a multiplayer paywall and many other players themselves play M&B for the multiplayer.)
The distinction here is that the single player can stand on its own merit.
On the other end of the spectrum, Left 4 Dead. I'd say that it would not be able to stand on its own merits in single player, due to the poor bot AI. 1 or 2 bots are ok, but having all 3 bots really suck.
So yea, the idea is, devs integrate tons of multiplayer to the game for the full experience. But, it gets locked out when you don't have access to multiplayer.
Subpar single player game that isn't worth the 'full price'.... and then they ask for more money to access the integrated multiplayer features for the full experience?
>
Ninjas, Man of Paper has the same idea as I'm trying to convey.
EDIT: I suppose this thinking does not apply to MMOs and similar that are marketed as 100% multiplayer only.