I would have rather seen something like this:
1. Illyria is not weakened down and still has her ability to open portals to other dimensions.
2. They use the tatooes Lindsay used that hid him from the Sr Partners, only they cover Angel in them instead.
3. Spike, Illyria, and the rest go through the portal to fight the Sr. Partners and their army, posing a threat to the Sr. Partners and drawing their attention. They have their big and epic battle against the army.
4. Meanwhile, Angel has been armed with some spell or weapon capable of fighting the Sr. Partners. Probably uncovered by Illyria or Wesley (I was thinking something in the Well where Illyria was sleeping with all the other ancient powers). Hidden from their view by the tats, and attacking them from behind while their concentration is drawn by Illyria and Spike (the obvious threats in Angel's group), Angel manages to basically assassinate the Wolf, Ram, and Hart.
5. An interesting way to wrap things up from there would have been to have the Powers above offer Angel his humanity as fulfillment of the Prophecy. An even more interesting way to end things would be for Angel to then decide to pass it up, and tell them to offer Spike instead, who unknowing that it was first offered to Angel, accepts thinking he earned it for his role in all this (which, to a lesser degree, he has). Angel then takes the rest of his team (those that survived), and goes back to running Angel Investigations or maybe starting a new firm (or returning to WR&H, but starting it as a force for good, which is what he'd hoped to do anyways) and continuing to do what he wanted all along - fight the good fight, and help the helpless.
They could have still killed a bunch of people, but the show would have ended on way less of a down note.