I don't know why, but it seems Rayman automatically shifts his focus to the Hoodblaster near the cave after you've taken the Green Gem and rolled off. Way back, I tried to use this exact start to improve on the classical Green-Gem-Combo by at least getting both Hoodblasters for 1.000 Points in Combo, but I couldn't even break the first Piggybank on the ground in time (I've tried to change the angle to avoid focussing on the Hoodblaster, but it lost too much time). I've had the same idea as you (although without using the 4 Yellow Gems at the top), and briefly considered just taking the Green Gem as item No. 15, then killing one of the Hoodlums, and getting the Tribelle for 2.000 Points; but then I would've had to split up the Combo again (which would've kind of defeated the purpose), I would've lost those 3 Yellow Gems from the Piggybank on the floor, I wouldn't have gotten either Hoodblaster for 1.000 Points, I would've had gotten less Points from the Hoodboom, etc. But thanks for the idea anyway!
To top it off, the way I wanted to play it with the first Tribelle for 1.500 Points in Combo turned out impossible thanks to that stupid Hoodblaster standing in the wrong spot. So now I'm back at the beginning - the first Tribelle and the Hoodboom are both taken in a seperate Combo. I guess this will have to do for the time being.