... vs Imperial Knight Warden

[Hendrik Booraem VI]

So, a friend and I are going to split a copy of Imperial Knights: Renegade and I intend to make one of those super-overpowered Knight Crusaders.

Plan is for the Knight to look like this:
Rapid-fire Battle Cannon
Avenger Gatlin Cannon
Heavy Stubber
Icarus Autocannon

I have started a WH40K group where I work (small state college in the USA) and we meet most Thursday nights during the summer to play small battles based on a campaign we're working through (of our own design). Mostly we fight 400-1000 point battles, using Adepticon 2013 Combat Patrol rules for the 400 point battles, and some house rules for the larger battles.

I want to add to this a scenario where each army present has to face off against this single Imperial Knight Crusader. The various factions will have a 500 point army, the Knight will be as listed above. The battle will take place on a 4x4 table. Right now I'm leaning towards a simple face-off between the two, although I might add in objectives for the Knight to destroy later.

The Space Marine Army list I'm considering taking is:
Iron Hands
HQ: Techmarine w/servitor
Troops: 5-man tac squad w/ML x2
Fast Attack: Land Speeder w/multi-melta
Heavy: 2x predator w/TL LC

We also have Tau, Orks, Tyranids, Chaos, and Adeptus Mechanicus, so I'm working on an Army list for Tau, Orks, and Tyranids. Thoughts on this list, and on what the Tyranids should take?