I’m not quite sure I understand what you’re trying to say.
Do you mean you want a script that shows katakana for an on- reading and hiragana for a kun- reading, like some dictionaries do?
If you want to type onyomi readings in katakana, normally you would just use caps lock - but I’m pretty sure the system will not accept the answer as correct (in specific cases items allow for katakana input but those are always listed as ‘alternate’ readings).
Any script that displays hiragana as katakana would then have an issue because you wouldn’t be able to recognize any differences between an accepted answer (hiragana displayed as katakana) and a rejected one (actual katakana displayed as katakana).
Unless this is not what you meant - there is the katakana madness script, but it does not mess with review-input.apparently it does change review input, see further down