This has probably been posted already but...
In the interest of balance I beleive that no profession should be restricted to one set of Symbiants. There are some professions that can access two or even three lines so I'd propose opening up another option for those professions that can currently only use one symbiant line.
OP'd?
Thinking along the lines of-
Doc - Support and Art
Engie - Control and Art
Soldier - Art and Infantry
Enfo - Infantry and Support
Agent - Art and Support
NT - Exterm and Control