ooooh nice idea
but i thought of an upright walking huge Kroot, using a Krootox head adding the 'hair' with Greenstuff etc.
edit:
@Tael: i like to combine parts of the Kroot-Guns and their 'new' weapon (like the Flamer and the Plasma) it gives them a bit more Kroot'ish look and it can count as a Knife (even though knives don't need to be displayed).
think about it, Ganger1 runs towards the Kroot with flamer, pushes the flamer aside, the Kroot pulls up the gun and pierces the Ganger with the flamer blade

those kroots are nasty bastards

okay i hope this one is big enough (or atleast bigger)

1. WiP Kroot (Assassin?) 2. 'Man-Kindred' Kroot with Flamer 3. Heavy Kroot with Plasma gun