You can change the curve of the envelopes by applying recursive modulation in the MOD matrix.
You mean Modding the "Amp envelope" or "Filter env" with itself? In that case you loose a lot of slots just to cover the filter and Amp envelope.
Exactly. You need two MOD slots, one for the Amp the other for the Filter. Most of the time you probably won‘t need to modify all of attack, decay and release, and you can use one or two other targets.
Start experimenting with it. I found most of the time it‘s sufficient to modulate the attack and/or decay of either the filter or the amp envelope to get the desired feel. Which meant I needed just one MOD slot and could even use one of the targets to modulate another parameter. You could, for example, use just the Amp envelope and modulate the filter with that as well.
Anyway, that‘s a lot more flexibility than just switching the envelopes from linear to exponential.
On further contemplation and remembering how I used it, there‘s another downside to this aporoach: It seems that the recursive modulation is quite calculation intensive. I found that a simple patch could go from one bar to three bars on the CPU meter by just adding modulations for both envelopes.
Thus, it would be great to have the opportunity to switch the envelopes to a more economic exponential behavior.
Also, it would be tremendously nice to have the switch available for every phase (attack, decay, release) of all 4 envelopes. 
