If we're speculating on what hypothetical wave two MW toys would have been, we need to look at the early 90s Euro G1/G1.5 moulds and anything from the tail end of G2.
It's always possible Hasbro would have dug deeper for moulds had MW proven to be a success, but for the purposes of keeping the "spirit" of what it was, I think those are good starting points.
So with that said? I think a good base mould for a hypothetical MW Bumblebee is
G1 Boss. He wouldn't have had his missiles.
Colour scheme may seem random but there is a method. Machine Wars figures were all gang moulded. The weirder aspects of the line- such as Optimus' and Prowl's olive green- were the result of those parts being moulded along with Thundercracker and Sandstorm. It's likely that any G2 wave would have its own collective gang moulding and not be reliant on the wave one layouts but, again, let's use that as a basis to keep the "spirit" of the line alive.
Wave one had Hubcap and Skywarp's head so we know yellow was in play. Still, yellow for Bumblebee seems too sensical for MW. So instead I'm going to look at the reddish brown plastic used for Soundwave's shoulders, arms, and chest, and Thundercracker's shoulders and thighs. That's the colour I'd use for Boss-as-Bumblebee's base, the light blue on the original figure.
I would use the yellow from Hubcap and Skywarp though, using it for the dark blue used on Boss' upper arms, thighs, head, and gun. I'd use the translucent blue plastic from Sandstorm, Starscream, and Optimus' windows for Bumblebee's windows and robot head light piping.
And as the cherry on top? Boss' greenish stickers would be turned black, ensuring that they blend into the dark reddish brown base body. Now that's a Machine Wars Bumblebee.
Thank you for coming to my TedTalk.