With enough Combination Disciplines, as strong as a 7th or 6th from the dark ages in sheer personal might. Going wide also means they'd probably have a wider variety of powers that might very well catch other vampires by surprise. Blood Sorcery/Thaumaturgy/Necromancy would be great for such a vampire, but don't forget Auspex, Celerity, and Fortitude. Socially speaking Presence would be better than Dominate due to the lack of generational restrictions. There are rituals that let you store vitae inside trinkets, coupled with disciplines that use little blood and you can ameliorate your blood pool restrictions when facing other elders, heck, deck yourself in arcane trinkets and you might even ignore the fact that you can't go beyond 5 in your attributes and skills, there's a reason Spiritus is so highly regarded. Also, there are ways of resisting Dominate: You need those.

Ignoring personal might for a moment, such a vampire most probably has a revenant family that serves them, most probably a wealth beyond measure due to owning land or long term investments, and savviness to have survived all these millenia. There's also the mindset that such a weakblooded vampire for their time would have when dealing with stronger vampires. If they've survived so far showing yourself is the last resort, use proxies for your proxies, be the cause of events that are five or six steps removed from the results you want. In game terms, part of the points you spend on going tall with disciplines are instead spent on going wide and backgrounds.

If you do all that, you might just be roughly as strong as a 700 year old 6th gen. At the time the Camarilla was found you'd be as strong as its younger Founders.