I've always figured that to have an "All Gnoblar" list with some level of close combat ability and still keep Ogres out of the picture; maxed units of sabretusks would be the only option. I could imagine some Gnoblars desperately clinging onto a sabretusk's back, others cleverly strapped on and using some kind of long pointy prod to goad the sabre in the right direction.
I'd be keen to see someone have a crack at such a conversion.
I just see a bunch of gnoblers on some kind of rig, riding a Mournfang into battle. You know, the big baskets on elephants with four or five archers up there... but instead of four or give gnoblers, it is as much as they can cram up there, and they are armed with anything from pistols, to angry hedgehogs.