Hey there!
From my first read through, these rules look pretty sweet! I do have a few Q's though, so please bear with me... I'm a big fan of 40k and necromunda, but I've never played Mordheim, which these rules are based on, so please forgive me if I ask something that is actually quite obvious...
First - why can't Krootoxen gain experience? I understand for things like Kroot hounds and Slaaneshi fiends, which are animals and beasts, but a Bloodcrusher can gain experience, as can a Rough Rider, and a Krootexen is, like these, as much a mounted rider as an animal or beast...
Second - what does 'movement enhanced' mean? I Can't find any definition, and the only thing it seems too apply to is that each army is limited to taking only a certain number of models which this quality. Does it have any other meaning than this? Also, it seems to be applied inconsistently... in that some models with jump packs or bikes are considered to be movement enhanced, and others are not, and no beasts or cavalry are ... I don't know if this was intentional or not... if it was, why did you choose to do it like this? It is rather confusing...
Jump troops that do have ME
-Assault marines (all chapters)
-Seraphim
-Raptors
-Swooping Hawks
-Warp Spiders
-Vespid
Jump troops that do not have ME
-Crisis suits and Stealth suits
-Flamers of Tzeentch
-Chaos Furies
-Hellions
-Swooping Hawk and Warp Spider Exarchs
-Wraiths
-Stormboyz
-Gargoyles
Bikes that do have ME
-SM bikes (all kinds and chapters)
-CSM bikes
-Eldar Jetbikes and Shining Spears
Bikes that do not have ME
-Screamers
-DE Reaver Jetbikes
-Necron Destroyers and Heavy Destroyers
-Ork Bikers and Deffkoptas
Thanks!