I am very interested, and actually did a tabletop roleplay of orks with my buds a few years back. 

I agree to some extent of how everyone starts to play the same character at first, but gradually it changed because of ork 'classes.' As long as everyone is playing different types of orks (Mek boy, Painboy, Freebooter, fereal ork, Nob, etc.) and makes up their own individual goals, then the rp could work. 

Another thing I'll say is that we played with Deathwatch core rules, and had the orks "working" for a inquisitor (Example: The orks are sent to some Imperial planet under the sway of the Tau, the inquisitor sends the orks to start trouble and disarray before the imperial forces show up to squash the rebellion). So the group is not with a giant ork Waaaagh, but a small group, under the heel of the inquisition, though as you can expect shenanigans to start happening very quick.   

The skies the limit for orks though, there are so many clans, and types of orks that everyone can easily play a ork with it's own distinct personality. Just need to know the lore more or less!

It's not impossible is all I am saying, and I am more than willing to Gm. Let me know!

PS: It's ork, with a K!