If, possibly a big if, Hartley is still interested in performing, I reckon he'd be a good "mentor-like" figure for the likes of the young loons Fyvie, Pawlett et al.
Yes I utterly despised his minky-cheating ways for celtic and the mini-huns, but he probably is the kind of "experience we need in the middle of the park.
The fact that it's from the rumours site means this is, in all likelyhood, merely pointless conjecture.