(I should have asked this before)
Do you already have such a LED device? How do you currently enter the
text it displays?
Maybe not - you can 'send' the document to PowerPoint from Word and each
paragraph will be assigned to a slide. You can then format the slides to
give the result you want.
That presumes that the libretto/text is available as a Word document.
Even then, the slide version in opera needs heavy editing: most sung
repetitions are omitted from the surtitles.
But the main effort surely must be to tie the projection into the
computerised cueing system for the timing.