There is a mod for TES V Skyrim which increases one's vampire skills the more people one feeds on (boosting one's speed, damage, armour, weapon speed, etc.).
Here I was thinking about adding the following mechanics: increasing damage based on the amount of people one has fed on by up to 7 (or 9 – such a lovely Nordic number, don’t you think?

) per cent. It's a lot, but it is to come at a cost of perseverance – so as not to be that easily attainable. Also, maybe the damage can be added to weapon (eg. physical gets up to 9 per cent weapon damage as poison or disease, whereas staves get magick damage).
When would the counter start? Since the Greymoor chapter ofc, when else?

The numbers – milestones – suggested can be the following:
0 per cent – fed x 0-99 – Newborn Vampire
1 per cent – fed x 100-399 – Initiate Vampire (+300)
2 per cent – fed x 400-899 – Awakened Vampire (+500)
3 per cent – fed x 900-1599 – Ascended Vampire (+700)
X+200
4 per cent – fed x 1600 – 2599 - Blood Knight (+1000)
5 per cent – fed x 2600 – 3899 - Blood Duke / Duchess (+1300)
6 per cent – fed x 3900 – 5499 - Vampire Elder (+1600)
X+300
7 per cent – fed x 5500 – 7599 - Vampire Master (+2100)
8 per cent – fed x 7600 – 10199 - Night Scion (+2600)
9 per cent – fed x 10200 – 13300 - Lamae’s Chosen OR Nosferatu OR Drakul (+3100)
X+500
Should ZOS consider this, I'd leave the adjustment to them – numbers and titles alike. Honestly, I don’t know whether I have ramped up the numbers or not…
One would have to feel that he / she HAS achieved much by draining SO many people (bear in mind, we still have to feed, don't we – no longer to reduce to stage 1 to be less vulnerable to fire, until you reach stage 4 with perks), hence an achievement could have been introduced and connected with that – say, every three per cent.
Alas, in order to get this final percent, and perhaps some extra boost to skills, one would have to do a solo quest, perhaps longish / shortish, just like with the quests for vampire / werewolf.
So, wouldn't such a character be OP? If he / she attained such a level?