I think everyone's getting a little carried away here. We can let the OP decide what kind of blues he wants to play without jumping all over him insisting he be a purist, can't we? The blues can be a lot of things.
To the OP, I think the main issues to think about have to do with the dynamics of the group. Personalities are more important than chops. Everybody doesn't have to be best buddies, but avoid drama queens and look for people who are professional enough in attitude to learn their part and do their job and not tear things apart.
Talk goals and make sure you understand WHY each person wants to be in your band. Some may want gigs and some side money, others may be blues purists, others may just want to entertain, etc... Keeping the band going means making sure everyone's goals are compatible and everyone is getting enough of what they want to stay motivated.
Assuming you plan to gig, invest in the best PA you can afford. Invest in marketing - social media, a website, a banner, business cards, photos and video.
Set a timeline that you want to be out gigging by. Start looking for bookings as soon as you can. Don't spend a year in the basement trying to get everything perfect. The perfect is the enemy of the good. Nothing will motivate people to get off their butts and pull together than a gig on the calendar they need to be ready for (the right people, anyway).
This. OP isn't starting a church, he's starting a bar band. Lighten up people.
If you play old, traditional blues for four hours straight anywhere other than a few major metro areas (Kansas City, Memphis, Chicago, etc.) prepare to stay at home most Friday and Saturday nights.
You absolutely can stir in some SRV, Delbert McClinton, Allman Brothers, etc. In fact, you would be wise to do so. It would take a very special audience to be mesmerized all night by the list of traditional blues artists that have been listed here. I love blues but couldn't sit through that all night, even if the players are great. Remember, you are asking musicians what they think here, not club owners or audience members.
Do yourself a favor. Watch this scene from Jod Dirt when you are not at work. It will clear up everything with regard to marketing....especially the last sentence.
Remember the two goals of any band.
1) Entertain the most people possible most of the time.
2) Make money for the person who hired you by drawing a crowd that buys tickets and/or keeping a crowd that buys food and drinks.
I doubt very seriously you could accomplish either in most towns by sticking to the hardcore list of "rules" you have been given here. The is bar band logistics, not rocket surgery.
Yes, the drummer can make or break this kind of act. Yes, guitar (or harp) wankery for ten minutes each song can make for a boring night for your audience. Yes, the front man/woman is the sun around which all other planets in the band revolve. But, honestly, these can be said of virtually any band.
Keep the goal in mind. Sell beer or tickets by entertaining the crap out of those who come to see you. THAT ALONE will keep you booked as much as you want to be. Sticking to traditional blues rules will not.
And,honestly, as neat as this is, it won't accomplish the goal. You will be stuck doing this in your basement.