What do you mean by "have control as a modifier"? There are… lots of modifiers. They can't be collapsed into one control key.
UEB has multiple modes (numeric, capital, grade 1, etc); multiple contraction prefixes (e.g. dot 4 S [dots 2-3-4] = $; 5 S= some; 4-5-6 S = spirit; 4-6 S word final = -less; 5-6 S word final = -ness); stand alone word signs (e.g. S surrounded by space or other stand alone signs = so); etc. And with 8 dot braille, adding dot 7 to any of those (if word initial) makes first letter capital.
It's not possible to do UEB in a context free letter by letter manner. See e.g. liblouis.org for an open source implementation.
And control s is "save" in lots of software. Control and other modifier keys are just as needed with braille input as any other. (More so, because we also need an extra modifier key for interacting with the screen reader — usually caps lock is hijacked for this — and it does combine with other modifier keys too for various commands. And yet more chords for e.g. scrolling, enter, arrows, cursor manipulation, etc.)
And that's just UEB. There's also Nemeth for math (which is a sub-mode of UEB). And lots of different codes for other languages, IPA, music, etc (which are also all sub-modes of UEB — there're encoding-change word/passage markers). And yes many characters are different by context, like ? / “ (and they can be overridden using modifiers, eg 5-6 2-3-6 = ? even if word initial). That's not just quote; there are tons of such cases.
And there are a bunch of standard contractions, like brl = braille. Those are part of UEB.
And output change modifiers, eg if I want to output English text vs Unicode braille…
Meaning no offense, but… have you gotten any blind people to test or design this? Your description seems to indicate rather basic misunderstandings of how braille works. Makes me concerned that using this would not actually work at all, let alone as a braille input device that needs to interact with my screen readers on Android, Windows, & OSX. 😕