Some tricks can be done by using a second envelope (e.g. MOD -> EG1) and add / subtract it from the OPs envelope using V.PATCH (assign it to OPx, Level and Intensity to +100% or -100%).
I haven't been able to let them cancel each other out using an attack against a decay. In other words: the attack of the OP is 1000ms. The decay of EG1 is (default) 1000ms. Assign EG1 with -100% to OP1 level.
Theoretically it would start with a level of -100%. Halfway the envelope they would both be at 50% (crossing point), so the output level would be 0%. And then it would start fading in.
Turned out this doesn't work; they are multiplied by each other, not subtracted.
However there is one thing that may help you; the sustain levels do seem to be subtracted from each other. Example:
OP1 (or any other, doesn't matter):
Attack: 0ms
Decay: 0ms
Sustain level: 50
EG1
Attack: 0 (default)
Decay: 7000ms (something long)
Sustain level: 0 (default)
V.PATCH
Source: EG1
Destination: OP1 sustain level
Sustain level: -100 (lower than -50, the negative of what you picked as sustain level for OP1)
For the sustain level in the V.PATCH, it must be at most the negative number of OP1s sustain (-50) to start in silence. The lower value you use, the longer the delay in the attack. Double the value (-100) means that half the time of the attack will be silent, thus delayed.
There are limits here since you have to sacrifice the actual decay of the envelope, but hey, it's a start
