so i finally remembered to look at this after work. You're right Env 1 is hardwired. The way I'd been working around this was just to turn env1 attack all the way down and sustain all the way up, turn the osc sections' volume knobs all the way down and use different envelopes to modulate the volume knob per oscillator engine.
For the most part that should let you set up different envelopes for the different osc sections. just make sure the env1 release time is as long as the longest release on the other envelopes.
Does that solve the problem?