OP here.

I'd presume that someone who is better versed in wall-street style algorithmic trading could speculate better than i what a mature cryptocurrency trading market would look like.

I'm curious to see what a mature market in this space looks like. It'll surely be different on a currency-by-currency basis, because volume, market depth, and fundamentals matter greatly and are unique on a per-currency basis. Time will tell.

As to whether profitable automatic currency trading competes with mining for compute time, I posit the following question to you: Are the two mutually exclusive? In a world with (1) scalable compute power via AWS, Digital Ocean, etc, and (2) both are profitable, why not do both instead of one?