More 11th brainstorming, this time with the Bastion Task Force using Blood Angels, which I like the sound of. Two ideas, though I can't post any images because I think that's what flagged my account with copyrightable rules but I think most people can find them out on the net either way (and GW put Bastion Task Force online below) so..
First idea:
Librarian in Tacticus Armor Hero of the Chapter (Leader)
Ancient in Tacticus Armor Eye of the Primarch (Support)
Squad: Desolation Marines all with Superkrak Launchers
Sanguinary Priest with Assault Intercessors on foot Blades of Valor
The Librarian now has Battleline as the keyword which allows all in his squad to be Battleline. Ancient attached which can still take enhancements grants Precision to his weapons but also all his squad.
Which means the Librarian's psychic powers now has Precision, and all the Superkrak Launchers have Precision. At 46" you are going to be sniping big fucks and being a mortar team for smaller fucks. Just be sure to screen this unit.
Precision for those who don't know, allows you to separate attacks against either character or that character's unit. You can in this theoretical case allocate all Superkrak missiles to an individual character.
The second idea:
Sanguinary Guard all Lances with Jump Pack Captain Hero of the Chapter
Librarian in Terminator Armor Eye of the Primarch
Sanguinary Priest with Assault Intercessors on foot Blades of Valor
Sanguinary Guard having all Lances with Jump Pack Captain and Battleline means with your special rules they can fall back and then immediately slam back into whatever they want to kill with a 2 to the wound roll.
I think having the Sanguinor here with heroic intervention would be a good bulwark to control the flow of the battle. A trick I've heard people do is put him 2" behind an enemy you charged so that they can't do a pile-in and if they counter-charge they have to go through Sanguinor
Librarian in Termi Armor doesn't bestow the Battleline bonus to his unit but his combi-weapon and his psychic powers DO get Precision. Which means he can absolutely mindfuck individual characters. If it's an infantry, he can use his combi weapon on it instead. Apply with an Assault Termi squad in proper Blood Angels fashion
Finally the last one is for both ideas but pretty standard and cost effective: Sanguinary Priest provides -1AP to his unit so he has -2AP Astartes Chainsword and gives his unit -2AP Astartes Chainsword. Apply Blades of Valor and everyone has -3AP Astartes Chainsword. Like having cheap Bladeguard, except more numerous so it should mince up some elites and keep trash at bay
The rest of the army is Baal Predators Intercessors (with Sanguinary Priests) Heavy Intercessors, no leaders individual Captains running around
A good mix of melee, gun, armor and speed, can only have 3 enhancements and Bombast Vox looks like shit if you're relying on RNG