Hmm, as a registered developer I am very reluctant to jailbreak -- the Apple developer agreement holds us to some very strict conduct and confidentiality requirements, which it's fairly important to respect when it's your livelihood! I can't afford to have my Apps or client's apps pulled from the store...
It's probably more wise to continue to pitch a case for optimising or supporting gestures that do work well on the 1st gen devices. Such as leaving out the left/right gestures, but leaving in swipe up to reveal multitasking bar and pinch to home, which I assume are less processor intensive: "assume" being a key word here. Surely allowing the user to choose is a good compromise?
AssistiveTouch is at least helping me avoid a flurry of double-clicks of the home button, which in a quiet environment gets on the nerves of the people around me. Pre-multitasking gestures I found that especially in bed I was making a flurry of home button "CLICK-CLICKS" repeatedly copying segments of text between and referring to 2 apps like a mind mapping app and project management/flow charting app.
Now being forced back into the "CLICK-CLICK" workflow -- ergh!