Well, for penmanship to improve, one needs to consciously make an effort to write a certain way. I used to get annoyed with some of my very young EFL students because they were in the process of learning penmanship and would take forever to write in a gorgeous, scrolled style which is great in general, but not great for speed games aimed at reducing processing time. I like this idea, but I have to say that I have some seriously atrocious handwriting. A lot of people say this, but more often than I'd like to admit, I spend time puzzling over what I've jotted down. Anyway, it sounds like it could be fun and constructive. I like the idea of parameters too.
Hopefully this would help with your writing then! We'll probably have a vote to seeing if people want it random or within those parameters. So far most seem to like the idea of random pairs.