The problem with any/all solutions to this problem is that of acceptable usage. For example, there are technical documents who would refer to SCUBA but travel brochures that would refer to scuba. Similarly scientists work with LASER but companies sell laser devices.

You cant create rules about pronouncability because both 'laser' and 'scuba' are pronouncable. 'Sky' contains no vowels and so might/might not be an acronym. Qantas contains no 'u' after the Q, nor does Iraq. Qantas is the "Queensland and Northern Territory Aerial Service" however, noone uses that outside of a trivia game these days. Its considered a word. Iraq, of course, is from another language and doesn't follow English rules.

Databases like vera can help you with a list of known acronyms but in Real Estate advertising 'LUG' is a lock-up-garage whereas in a mechanical journal a 'lug' is a type of nut.

Given all this, when parsing user text I normally require that there be one or more lower-case letters in users input. That way I know they didn't just type it with the Caps-Lock button on. If it's all in capitals I'll ask them to change or confirm what they've entered.