My concern is how to keep them readable today!

The syntax of English has not changed too dramatically between Shakespeare's and Stephenson's times. The vocabulary and the meanings of many lexical items more so. I'd say the biggest changes have been in the cultural and knowledge areas. So while I can imagine that Shakespeare might, with some ramp-up time, be able to "read" Snow Crash, he probably wouldn't understand a lot of it.

The same holds for Stephenson reading Shakespeare (or a lesser known Elizabethan-Jacobean writer) without modern editions and critical apparatus.

Ceci n'est pas un seing.