I agree Cantman's response to what the pros and cons of messing around with "gas pedaling" are. Was this your question or did you mean pros and cons to making the change by raising the toe and countering the toe lug to fit into your boot?
The easiest way to figure out whether you need change in your positioning either with ramp angle change internally or externally is to test it.
External lift is the easiest to do. Take a 3mm shim ( I use 3mm bontex shims).
Pick your favorite terrain take 3 runs with the same line and varied turn shapes. 1 run with the shim between the boot toe and binding AFD. 1 run with the shim between the boot heel and the binding heel piece. 1 run with the shim removed.
Repeat this test 2 more times on different terrain or snow. I would also check out the differences on your GS versus SL skis. At some point in the process something will feel better and something will feel worse. There are 4 possibilities:
1. You will like the toe externally raised
2. You will like the heel externally raised
3. You will like the boot just as it is
4. You will be so confused that you will have to quit skiing for the season
Before you do this, I would recommend that you find your bootboard ramp angle first. You can test this in the same way.
You can do this same test with internal ramp angle by raising the heel 3mm, or raising the toe 3mm. Perform the test the same way. A little harder to do because you have to stop take off the boot, insert or remove toe or heel lift, etc.
In terms of order, I would always figure out your internal ramp angle first, and then figure out your external changes. Be consistent with binding ramp angle as this will have effect on the outcome.
You have read sources that describe the Diablo Race Pro as having excessive forward lean. IMO Excessive is a relative term for boot forward lean. Relative only to the individual that is inside the boot, not the dimensions that you read on the company brochure. The Diablo Race Pro is not the least in forward lean, and is not the most in forward lean. For some skiers it will feel like too much forward lean, for other skiers it is just right, and for others it will not be enough. The Diablo Race Pro also has a bootboard that has a little lower ramp angle then other boots in that class. This adds to the feeling that this boot forces you forward. By changing the internal heel height or internal toe height for that matter, you can alter the feel of the forward lean on any skier.
One other point is lumping all bindings of a brand as being the same ramp angle. All models of the same brand are not the same ramp angle, as well as model years within a brand can be different. ("running changes", this is when a manufacturer makes subtle changes in production and runs away without telling anyone) Also there are manufacturers that have made adaptations to some ski models and plates that change the ramp angle of some models of bindings.
Maybe more info than you wanted? So here's the simple answer:
Gas pedaling - could work as a way of straightening up the lean of your boot.
Gas pedaling with an external Boot Lifter - the preferred method of implementing the gas pedal effect - allows you to step into any ski with the same feeling.