It’s not always so bad as you’d think: Don Quixote was first translated to English in 1612, for example, but is still perfectly readable (so long as you don’t mind exceptionally-long and flowery sentences and a handful of pieces of terminology that have since left the popular lexicon). Shakespeare’s earliest plays were published around 1590 and, again, are quite readable (especially with a couple of interpretative notes to help provide context).

Very early texts in this period are harder specifically because English was less-standardised at that point, and more-inclined to be written phonetically. In many ways, the development of the printing press seems to have had a huge impact on standardising English spelling, and so only a hundred years later the printed word exhibits far greater comprehensibility to modern readers than it did before then.

There are no such academic efforts that I’m aware of, but now that these texts are available in the public domain there’s nothing to stop such an endeavour from being easily crowd-sourced: it’d even be possible to do some kind of computer-assisted crowd-sourcing, where a computerised dictionary helps humans to modernise old works. Hell – if you wanted to run such a project, you can submit your proposal to my employer for a chance to win a prize. Just sayin’.

Note that I’m a computer programmer and (very definitely) not a linguist nor a historian, so some or all of the above might be complete bullshit. You have been warned!