Separate mgr context settings for TinyMCE?

Totally stuck on this one. I've got a multi-context site, and I'm using the main "web" context essentially as a JSON API generator. The other contexts will become homes for actual websites.

Here's my issue: because "web" is spitting out JSON, I want the rich-text editor (TinyMCE) to have a very limited button set (bold, italic, and maybe links) in that context, but that context only. The others should have the full "advanced" set.

Simple, right? Just create tiny.custom_buttons1 and tiny.custom_buttons2 context settings for web! Except...that doesn't work. And if I'm thinking it out correctly, it makes sense why it doesn't work: "web", and all of the contexts, really, apply to the front end of the site. What I'm really trying to do is limit the "mgr" context, but I don't know how to do this, other than alter the system setting itself and then add the default settings back into all the other contexts.

Is there a better way?