Tarantulas from Transformers BeastWars is probably decently more on point to a warframe thinking.
The problem with a spider is their movement. What can they do that would be difficult to do in game? Wall crawling would be the big one. We can cling but not climb.
Tunneling is another but they could always just modify Hydroids ability. (think trap door spiders)
Beyond that... should all be withing the realm of the game to do. Cocoon, suck juice/blood, interesting leaping, extra legged looks (look at Titania wings and such.), stealthy hunting... Yeah, all doable.