I bought the game a few weeks ago after the add of annihilation and a reduction in the price, with a few tens of hours playing it I started to notice that from all the races featured in this game the orks look by far the ones with the funniest gameplay and missions, not only that, the whole aesthetic of the game actually works in their favour, with the cartoonish visual style, over-animation and silly voices giving them the right atmosphere both in line with the 40k canon and the ork previous tradition, even their music is very cool and fit their character extremely well.
From the ork's perspective they are basically having the time of their life, for them the galaxy is a amusement park where they are at home and doing what they know best, waging endless war for the fun of it. In a very amusing way this works great with the whole metagame of Dawn of War, people get a fight, have a great time, and they either win or die just to come back for another one (of course for everyone else PoV they are galactic menace, read The Beast Arises series for human PoV of ork Waaaghs!).
This makes the orks perhaps the best choice for further add-ons to the game, gameplay and campaign, since by this point we are stuck with the visual style and gameplay, what better thing to do than to make the best of it? For example resource wars where orks fight over scraps to make new units, ork-cannon galleries to hit moving targets, gladiatorial fights between ork 'nauts and similar games would be great add-ons.