This can be done already:
1) Allocate glide to one of the assignable collums in the matrix
2) Assign env to glide via the matrix
3) Leave the glide knob set at 0
4) Play with decay/release and sustain settings of the env and with the modulation amount in the matrix to achieve desired result
BTW: I do agree that a dedicated legato-glide option would make a for very nice (and easy to implement) addition on the microfreak...