No mate all 500 will come from troops you may include 1 fast attack choice but it will be at the minimum size and no upgrades.
Each model in the defending unit can operate as an individual unit on their own.
The Sgt of the unit will be upgraded to have 2 wounds and will have the units standard weapon plus a pistol and cc weapon . This is to signify the heroic nature of this individual, he may iinclude any upgrades as per their unit entry as normal.
Break tests. When the unit suffers enough casualties to incur a morale test the unit uses the Sgts Ld surmising he's still alive.
Deployment
No units may be deployed within 18'' of the trench for any reason. Deep striking troops will not enter within 12 of the trench.
Armor units, you may only include 1 non troop transport vehicle oh whilst on that no land raider transport for blood angels this vehicle may not have a front armor greater than 11
Cover saves whilst within the trench are taken at 2+ . However template weapons gain +1 st against models within the trench.
The Forrest offers 5+ cover save.
The swamp areas reduce all foot movement by half vehicles that cross the swamps will get bogged down on a roll of 1 or 2 they forgo the remainder of their move as does any unit embarked this unit may not fire this turn either this turn.
You can add some more scenario rules if you wish but I think you''ll find the above too be about right.
