This...sounds amazing TBH. A GW Hero style companion system blended with the companion system TOR currently has, would really hit the ball out of the park for a good feeling of control of your "personal Star Wars story" that EA likes to tagline SWTOR with.
The problem is that even player characters SWTOR are only just starting to get a taste of the robust customisation system that GW and moreso GW2 have built their MMO around. Companions would have to be totally rebuilt from the ground up to accommodate this, and then they would be more entertaining that our own characters, which is problematic. GW Heroes had customisable stat combinations for different styles of play (direct dmg v condi, health sponges v tanks v healer-tanks, specialised crit builds, etc.), and completely independent rune and sigil sets to further specify what you want characters to do.
TOR has...DPS, Heal, Tank. You could make the case that the bonus effect sets we have now are like runesets and the tacticals are reminiscent of sigils, but not only can companions not make use of these, they don't have the player movesets to use them, nor do we have stat diversification options to back them up. If they did, companions would likely be overpowered, and would really need to have their AI redesigned to make use of it all.
It's a great idea, but not feasible.