Vis-a-vis the theme changes you suggest, I have two concerns:
1) arguably the "best" option would be to have a button that would open something like EqEd (as we fiddled it to avoid the span issues) that would allow you to see the parsed code and the text expressions at the same time, which would allow the user to simply type the text expression with asciimath off, or click on the button, enabling one to see the interpreted expression in the popup.....
2) how the suggestions will work in the quiz module (both for the teacher and the student) and message module.
Before I can say anything about this cookie placement I should get more familiar with all the settings of asciimathml.js and the fallback code. Is it possible to avoid all error messages so that non functional code could be skipped without errors but could be debugged with some change of setting in asciimathml.js?
Code I am working with has I think all warning and messages turned off and falls back transparently to mimetex or mathtran; the cookie function has been added but not implemented while David in fact had I think actually deleted most of the warning features. Arguably one could simply not use the warnings at all and just advise that by default fallbacl displays will be in this color or font while display by asciimath will be in this font or color.... and for moodle use figure that it is up to the admin to address any warnings etc.... Or... provided a switch so that all the various tests (they are not done via a case type structure so that they are located in quite a few places) are anded with a universal on/offOne direction could be a larger downloadable package of tools for mathematics - for example a custom theme that allows using different editors and different plugins.
While I think access to more functions should be included in all editors a la xinha buttons as evidenced here:http://xinha.raimundmeyer.de/x_examples/ext_example.html
Providing a theme that has been specifically adapted for Math means that something more akin to what David and Peter had in mind might be appropriate, a la: http://www.pierce.ctc.edu/dlippman/HTMLArea/examples/demo.html
However, I don't think someone who wants to use asciimath should be required to alter their theme, and what happens when you are trying to share the contents of a course and one of the folks doesn't want the math theme....
by the way, one thing I suppose we could try to look at with your theme option for tinyMCE is reverse engineer the hover feature of asciimath.... at present hovering shows you the text expression, we could also try to do a quick bit check and if you are in the editor do a hover that is intepreted as MathML, but I think that is getting nightmarish