-At certain points in the game, Rinaldo Gandolfi is mentioned as being alive long ago - implies it is set AFTER Lament of Innocence?
-Also, a fallen brotherhood member mentions seeing Rinaldo alive? My theory is that Rinaldo is trapped in some kind of purgatory as a spectral being (which explains how he is in both LOI and LOS) perhaps linked to the Castle.
-In Gabriel's tome of knowledge entry, it implies he might be a member of the Cronqvist family, another reference to LOI (Mathias Cronqvist). My theory being that with Leon and Mathias being allies, the 2 bloodlines became 1 through marriage (not Leon + Mathias but their children!).
-Which brings us to the Belmont name itself (apparently chosen by Gabriel for his love of mountains? while it is Leon's name aswell ...coincidentally) this is something I couldn't work out, any ideas? Maybe when Gabriel was dumped on the brotherhood doorstep he had something that was a hint to his lineage on him, which caused him to discover his bloodline and take up the name later in life and use the mountain thing as a cover.
-A major reference to the other games of course is Olrox, Brauner and Carmilla. This is pretty easy to work out - they survived (not necessarily their physical beings, possibly in spirit) and were reborn, maybe part of the Castle's magic. Another tome entry that reinforces this is that the more feral vampires become more human looking the older they become- in Olrox and Brauner's case this explains why they look human in Symphony of the Night and Order of Ecclesia respectively.
-One of my favourite parts of the game is the final boss fight against....Satan, who in my opinion looks just like Alucard. I kept thinking to myself...why does Satan look like Alucard? Then it occured to me, he has black hair like he does in Castlevania 3! This could be in Alucard's formative years, and has yet to become a nice guy and is still a bad dude! So Alucard was posing as Satan to manipulate Zobec into gathering the pieces of the mask and giving him Ultimate Powaaah! (Power to fight his father- Mathias) One major reference to Alucard is when he says "do you hear me father?? now you'll take orders from me!". I thought he was referring to Drac at that point (although it was probably meant to be God).
How am I doing so far? I was pretty satisfied with myself for working this out! But then my face went from

to

when I watched the epilogue:-
So Gabriel is Dracula? WTF? But wait, let's think about this a second- the 3 lords of shadow were the brotherhood founders' evil side (a la Piccolo and Kami from Dragonball Z!

) am I right? Maybe that vampire is Gabriel's evil side after he ascended to a higher plane of existence. You do fight the last battle as an Angel right? Also, in that Epilogue movie Vampire Gabriel seemed pretty happy to lurk in the shadows, if he WAS Dracula, he would have fought about 20 generations of his descendants in the years between LOS and that point and been a pretty evil dude. Maybe Dracula is Mathias after all and evil Gabriel was just wondering the earth (like Lestat near the end of Interview with a Vampire, where he had been lurking in a run down building in New Orleans for years - the epilogue really reminded me of that scene!)
Also my theories have depended on one fact- that at the time of LOS , Mathias is still out there somewhere (has fathered Alucard with a human), and is gathering his powers still (not yet taken up residence in the castle- hence his current squatter Carmilla) for his war on God.