Firstly let me just say that I'm always a fan of people creating their own backgrounds/chapters for their armies and simply attempting to do so shows a great deal of creativity.
Also, let me say that in the end of the day it is your hobby, not mine, not frank's, but yours so, whatever I say or other's say, do what you want.
Unless you're playing Apoc, or have a group of friends who will let you do this, almost no one will let you use two codexs in one army. You need to pick one codex and stick with it, mix and match plastic kits, but not codexs.
Okay, so onto the fluff, it just doesn't work, at all, there are far too many fluff errors and also far too many incredible feats. It's always important to have something cool about you're army, but have too many and it lessons the 'cool' factor. For example, myself and many other people consider Superman to be a very boring superhero because he's got everything, he's too good, too hard to kill, there isn't risk, whilst I'm a fan of batman as he's got limits, faults, he's not the best at everything. Do you understand?
What you need to do is pick one or two 'cool' things and leave it at that.
As far as fluff errors, really there's almost no way anyone is getting at Grey Knight gene seed, it's about as likely as getting some of the gene seed used to make Custodians. Also allowing SM that have been soo exposed to Chaos is also likewise not really going to occur.
I think that you need to sit down and think about what you're really wanting to do with this army, if it's just about having the grey knight stuff with your blood angels, just mix and match the kits together and use them as a normal blood angel successor chapter, perhaps one tied in closer with the high lords of terra rather than the blood angels themselves, perhaps even a successor chapter commissioned by the high lords of terra to secretly monitor/spy on the blood angels and their other chapters, therefore justifying the extra =I= icons on their armour.
I hope this doesn't come off rude or condescending, like i said to begin with, creating your own chapter is a great idea, you just need to refine what you're wanting to do with it.