I think Black templar would be better allies, in the role you have for your allies.
I would take Lysander with a deathwing squad, he will then be able to deathwing assault. You want him close to the action to hit things.
I think to best make use of Lysander I would bring him in a drop pod with sternguard. Then use scout bikers as a homer.
You can then deathwing assault say 2 terminator units and the sternguard and make a nice mess of the enemy, before threatening assault.
You haven't much really shooting ability, 5 2 missile units will not threaten a mech army, as an example. You are a bit too slow to imagine you can force the enemy into
cc.
Explanation of my own terminator set up:
Serg. probably wants
SS/
TH, this is due to challenges. Trying to imagine who you will challenged by, trying to survive using 2+/3++ to then hit back last but with the mighty hammer will most likely be the best approach.
CMLs for EVERY squad. It is dirt cheap. Then you have foot slogging troops, against a fast army they will pop out of assault cannon range, what are you going to without a ranged weapon. Then it is very flexible, you have very few models so having every squad being able to fulfil every role, without much down side is very sweet.
Give him a
SS/
TH, as if this model is alive then the squad if fully functional
Chainfists are mainly only good for killing land raiders. Hammers will normally be enough to crack back armour.
Apothecary is crazy good.
FNP terminators
, the banner is cheap enough to be worth while and looks cool(and I have no modelling skills, also the apothecary also looks cool.)
It is easier to model these on
SS/
TH. I guess it is better to have them on different models from your
CML, as you want to spread your risks with precision shots.
Storm bolters. What happens in your shooting phase is that you target your missiles at some mech,
MEQ, boyz, whatever. 2 missiles are too good to waste, so will pick targets for them. Any storm bolters will have to shoot at the same target, it will mostly be luck if the bolters are in range and effective weapons. Stormbolters are not really that effective weapons, anyway.
A word about
LCs. Now most only take them vs. hordes. However, striking last in
cc is dangerous and
LCs improves your
cc ability.
Enemy hits after I4, the
LCs will reduce attacks going your way.
Enemy hits at I4, then the
LC can attack and then die, thus the models life was not in vain.
Enemy hits before I4, in general the extra attacks are more useful than the high strength and
inv. save.
With those bits took into consideration. You take mostly
SS/
TH because
inv. save is better than a few chance bolter shots.
