ah - that's why the two guys on the street (caller? and the Guard) started shooting at me.
I thought i messed something up - i used to go Cass' quest and then go work for them to get the bomber do the dirty work - hmmm well i guess i'll just take Cass with me to wipe the place clean. Wonder if she'll still be complaining.
Anything changed with the Crimson Caravan?
That is the reason they attack. The idea is they know you turned in evidence against them. Crimson Caravan are fine with me. Totally oblivious to the fact I've wiped out the family, lol.
There are two quests tied to the Van Graffs that are eliminated by doing the quest for Cassidy. And, you lose the only Energy Weapons dealer in the game, unless you are working the BOS quest line at some point. While you can get some energy weapons from other places, the Van Graffs are a one stop shop.
However, other than that, the Van Graffs are not an intergral part of the game and the shop's inventory is all yours for the looting. (assuming you don't mind the Karma Loss from grabbing most of the items. There is a plasma pistol on her counter that is not owned.
What I would like to see is someone else come along to run the shop if you do Cassidy's Quest. Strangely enough, the Crimson Boss seems unperterbed by this whole chain of events.
I only used Energy weapons for the 10k DMG achievement. Still I'd like a nice collection of them, and will not mind the Karma hit for taking them. 100 Guns, so I tend to stick to that.
Nice idea with someone else owning the store. I'm glad this will not interrupt my main questline. Thankyou CC.

EDIT - Turns out you don't even receive any loss of Karma when looting the store. It says 'Steal x' but I'm not notified of any Karma loss.