I've fixed the Bloodsucker DLC!!!
I've managed to alter it so that all the perks will REMAIN locked until you decide to purchase them. You can also CHOOSE to purchase the Bloodsucking ability, or you can KEEP the neck snap ability. It is also compatible with older saves, providing you use the save editor.
Seriously, this was about 15 minutes of work progress (probably stuck 4 hours overall into figuring this out, but then I hardly knew what I was doing) and an hour of testing, why didn't Volition do it themselves?
Here is the perk list:
Bonus Cash Boost 1 (Respect level: 2 Cost: 11, 500) Bumped this up to level 2
Bonus Cash Boost 2 (Respect level: 13 Cost: 17, 500)
Bonus Cash Boost 3 (Respect level: 34 Cost: 22, 250)
*Bonus Cash Boost 4 (Respect level: 40 Cost: 27, 000)
Bonus Hourly Income 1 (Respect level: 4 Cost: 3,500)
Bonus Hourly Income 2 (Respect level: 11 Cost: 10, 000)
Bonus Hourly Income 3 (Respect level: 20 Cost: 17, 000)
*Bonus Hourly Income 4 (Respect level: 27 Cost: 25, 000)
Respect Bonus 1 (Respect level: 7 Cost: 6, 000)
Respect Bonus 2 (Respect level: 15 Cost: 13, 000)
Respect Bonus 3 (Respect level: 30 Cost: 21, 250)
*Respect Bonus 4 (Respect level: 35 Cost: 30, 000)
Scavenger 1 (Respect level: 4 Cost: 3,250)
*Scavenger 2 (Respect level: 10 Cost: 9, 000)
*Vampire Neck bite (Respect level: 3 Cost: 5000)
*I increased the price on these by roughly the same increment as the previous levels, and put the level at where I thought they'd best be.
Edit: Also note that the regen bonus that comes with the dlc won't take effect until the Vampire Neck Bite perk has been purchased