I would really like to have a "research queue" and "build ship queue".
This is a great idea. I concur on both points.
Pathfinding should take into account ASTEROID fields or other areas
Not always, but often I will move a ship, and it will go into an asteroid and get its movement down to 1 for that turn. That can hurt in a crucial battle, especially when it's a troop ship.
[espionage], barely even use it now, for a few reasons. One being the escalating cost of new agents.
I mostly do medium galaxies, and unless I'm flush with cash, which isn't often in my obscene games, i have to stop after a few spies because they cost too damn much/take too long to give any value. I'd rather put the bc's per turn toward combat ship maintenance.