...//..... The line's movement itself tells you a lot as well, ....//....
-tells a good tender a surprising amount of information.
...//...Has anyone developed an expanded list of rope signals? ....//.....
Signal sets vary with agencies, mainly because different agencies have differing ideas of how they want to split the tasks between the tender and diver.
The agency I train with considers the diver to be a "dope on a rope" who's main job is to keep the line tight while conducting a regular pattern search of the area immediately in front of him/her.
Ice diving signals typically come from the agency's search and recovery signal set. So concerning your "diver-to-tender" list:
Freeflow: Get me out of here now.
OOA: Get me out of here now.
Snagged line: Diver can't signal this one, a good tender will pick it pick it up very quickly.
Entangled: Diver may wish to clear himself or signal "I'm OK but send backup diver".
Silt-out/blackout: No signal needed, most searches are carried out in zero visibility.
Line separation from diver: Tender will know, but the carabiner is taped shut before the diver enters the water to remove the temptation to go that extra arm's length to reach the object being searched for.
Medical problem: Get me out of here now.
Cramps from the cold water: Get me out of here now.
...//.....Can you add others to the list? ...//....
The tender directs the search from the surface, so the signal set is something like: (Stop/Tighten Line/return signal when OK), Search to the right, Search to the left, Search immediate area, Stand by, Come up. These six signals work for many different conditions and search patterns, most other agencies get by with fewer than six.