Writing as a skill has seemed to really be lacking in many games. Where many games may have in game writing, never as a skill. Another inspiration may be the size of the work. Just as with the Contract system that gets more complicated as you improve your skill, the length of the total book could get larger as you level your skill. Something else to remember in Elyria is that many tribes may not have a common written language so tribe centric focus may be the way you need to go.

I would just make it typing in weird configurations.

Ex. Typing in a second languange or a harder contract level:

1. This contract is proof of consent for the exchange of 10 ingots of steel for 20 coins of gold.

2. Uksl wkscsaowt ld pwqmn al orsentr dub xtr hugtysle ld 10 wqrtsb ld yrtsl xtr 20 asegs ld nbvm.

This isn't a language btw, i Just kept the number of letters the same for each word. The harder the writing (due to complexity, language barrier, etc.) the harder it would be to type. It would be the same as those transcriber tests, except it would get even harder.

PS - #2 refers to what the player would have to type in to get the message of #1 across for the clients. This would obviously not be the norm, but would be a way to increase difficulty when volume of text can be a limiting option (no one wants to write a FULL page of text).

PPS - If the devs have any interest in creating a language, then I would just use English and then a Caesar cipher. Creates less work for devs, but provides the same experience. Obviously, the difficulty of cipher could relate to affinity of tribe, etc.

I would propose several levels of mastery, with stages composing those levels.

So the first level would require learning your letters and how to write legibly, associating sound groups to letters and groups of letters, basic grammar/spelling, etc... second level would be where you learn your sentence structure, improve on grammar and spelling, so on so forth, slowly expanding your vocabulary and understanding of lingual structure to encompass more and more of your language and the different ways it might be used.

This way, writing would reflect the real world - there's only so much proficiency you can gain in the act of writing itself. Much of what comes later is understanding the language you use and the myriad ways in which it might be used. If there needs to be more content for language/writing, expansion into other languages and language structures would work (each with its own difficulty level and degree of complexity - Brudvir runes would be quite different from the Neran alphabet in a number of ways), though I'm curious to see how they handle legendary proficiency with this particular trade. Is it going to be simple language comprehension, or will the legal system be rolled into the writing system as well?