Yes, for my part, I would really hope for autocomplete. Even if it comes down to enumerating all the MBOOT_ whatsit in a syntax file for my specific language, I would probably be willing to go that route.

Alternatively, Sublime Text supports multi-select. Ctrl-F, mboot[^\s]*\b and alt-enter to select all matches. Then use the command palette to convert to uppercase. Or ~ if you are using Vintage. But this isn't as good as autocomplete.

Anyway I have remapped caps and I miss it occasionally when typing constants. Usually I just hold down Shift, or use ~.