Sorry if this reply addresses outdated points but since not every drell is affected/infected by Kepler's Syndrome a blanket racial penalty isn't really necessary, is it?

The primary issue I could see with Geth being a PC race would be the fact that Legion admitted that he was a prototype, designed specifically to infiltrate organic space and make contact with Shepard.

Continuing along the assumption that geth will maintain PC status a penalty towards charisma seems more appropriate since most races are downright hostile to geth and they are impersonal, let's face it, robots. It's within the range of my limited knowledge that most examples of constructs, at least it D&D, have a penalty to charisma because they find it hard to relate to us squishy organics.

Vorcha's healing may be better represented by a limited amount of healing per day(sprint healing from Monte Cook's World of Darkness). This seems like a more balanced alternative to a fast healing that is affected by your con mod.

For those curious SH functions as follows: You are capable of healing up to a set number of points during a single round, example 5, until you have healed a second set amount per day, example 20. Therefore with a healing factor of 5/20 you would be able to heal up to 5 hit points in any round so long at the total damage you have healed in the day does not exceed 20 points.