I also love Tali, she is well adjusted and knows Shepard better than any other Female in the game, even if her DNA is a bit odd.
I was thinking of several mods that put Shepard, Tali, EDI, Legion, the doctor and Samara as critical.
1. The choice of rewrite the "Heretics" causes the Geth FTL link to stop. Legion requests Shepard and Tali to help discover the problem. Note the Geth are critical to the next fight with Harbinger.
1.a Tali is sick from a toxic preganancy of two DNA types. Sumara helps by bonding with Tali and Shepard to stabilize Tali's twins with a triple helix, Asari, Human and Quarian DNA on a common sugar back bone. The doctor helps with cybernetics to boost Tali's immune system; Legion and EDI also help with new technology. As a result, Tali can remove the enviro suit and is a beautiful fair skinned woman, not nearly as deformed as the envirosuit seems to indicate. However, Tali needs constant treatment and Sumara pledges to stay, feeling that the twins are her responsibility too. Most Quarians see Shepard and Tali's childern as a key to Quarian survival - Seeing Tali w/o an envirosuit sends a powerful message! Will the Quarians protect the Geth or Fight?
1.b. Shepard and Tali take Legion and an EDI interface to Quarian fleet obstensively for Tali's Admiral review, but instead discuss peace and must stop a preemptive strike against the Geth while their systems are locked up. EDI releases Harbinger's plans captured from the data mining to Alliance, Cerburus and Quarians, and vids of the team taking down the Collector base to boost support.
1.c. The geth planets are difficult to manage due to VI automated defences that shoot anything. EDI can use her cyberwarfare, but must work actively with Legion to pass the defences.
1.d. The Geth return the Quarian Home World and offer to help restore it as restitution for helping them. The Quarian Home World is virtually destroyed otherwise, but I suppose the evil side could also rewrite the Geth Code. Ensalvement of the Geth will only repeat history.
Lots more any thoughts?