I was improving a bit the db functional tests page and ended needing the ability of create a disabled checkbox (disabled="disabled" attribute).
After looking a bit both html_select_option::make_checkbox() and $OUTPUT->checkbox(), I think it's impossible to "inject" attributes to those option tags.
Perhaps it would be interesting to add support to that (one optional 3rd parameter with name/value pairs or so on). And perhaps extensible to other elements too.
Assigning to Tim for his consideration. Ciao