The problem is I don't have a team yet. And if I randomly assemble a team without choosing the engine first..........I'll get 3 unity guys, 4 unreal engine guys, 2 cryengine guys, and 1 guy who works on some smaller indie engine.
That's really not a problem that you'll have to worry about any time soon, as it relies on the assumption that you'll actually be able to recruit 8 startup-worthy programmers in the first place :P Consider that in the US, the rule of thumb is that a tech-startup needs $10k per team member per month.
Most people cannot afford to work for no pay. The group you'll most likely be able to recruit are students who still live with their parents, as their expenses are minimal and their free time higher than a working professional. However, you can't launch a AAA game with a student team. You also end up with the issues that you're worried about, where they can't work together, can't tolerate other technologies, have unreliable work ethic, and are over-eager to sign up to projects but unlikely to deliver.
At a professional workplace, adding a junior programmer to the team actually increases the amount of time that your project will take, as you need to waste a percentage of one of your senior programmer's time to mentoring them and helping them develop into an intermediate / independent worker.
The people that you need for a start-up are the core staff of these professional teams. The ones that can transmute a graduate programmer into a senior games programmer over the course of a few years.
Those guys are worth $100k a year. For them to give up that kind of salary and gamble on some entrepreneurial adventure they've got to be a an extremely rare kind of crazy.
So your recruitment audience covers the inexperienced and the extremely-rare talented entrepreneur.
The former category will give you all the strife that you're worrying about, and don't actually have the AAA background that you're looking for anyway... So no matter how good your own secret sauce is, your project will also be a flop.
The latter category can actually build you this game... but seeing you're not bringing cash to the table, they can also do it just as much without you. You need to realize that you need these people waaaaaaay more than they need you. Even if your claims of ensuring a hit are 100% true: without you they can build and ship an inferior product, but without them you're stuck.
In a partnership with people who can actually build your product, you're the one who's value is suspect. Assuming you can actually find AAA game veterans who would be willing to quit their paying jobs and go unpaid for a year or more on the chance of producing a hit game, these people are much more likely to set up their own studio by themselves. Usually new triple-I ("triple-A indie") teams tend to be made up of people who have worked together before -- e.g. 3 people who all leave a AAA studio at the same time, who were able to do a lot of the business planning while in a safe job (while also spending 40 hours a week in the perfect environment to meet other talent) before making the decision to go independent.
Imagine the tables are spun 180º from your proposal. Imagine a group of AAA veterans have just quit Activision and formed a new studio to make a survival horror game in your town. Now imagine that you go and knock on their door, resume in hand, and propose that they bring you on as some kind of consultant to ensure their game will be a hit, and all you want is half the equity in the company, or equity equal to the three founders who will actually be building the product. That's a tough pitch. You would want to have one hell of a sales speech backed up with some amazing data to win them over. With no track record or experience in game design, it's a really hard sell.
That's a tough challenge to take on.
But you're proposing to take on more than that -- you're trying to convince these people to form a new studio in the first place, without having the benefits of networking that comes from working at a large studio, or experience to prove your worth, or money to fund it. That's the above challenge x10.
Soo.... if I were you, I'd put this plan on the backburner for a while and focus on something more achievable: a non-profit venture to test the waters. When there's no money to be made, so many problems fade away.
You're not offering money? You're not making money - it's a hobby / passion project!
People get excited and join the team but don't contribute? No worries, you're not paying them!
Can't figure out a fair way to divide the spoils? The spoils are bragging rights - a credits list. Way less drama!
Can't convince AAA veterans to quit their jobs? Maybe they can spare a few hours on the weekend for a hobby they're interested in.
Can't afford to get the engine you want and all the basic assets, such as worlds / props / animations / sound effects required to boot-strap the project? Make it as a mod for an existing game!
e.g. DayZ started as a free mod for Arma 2, leveraging probably a million dollars worth of assets that existed in that game already. Once the mod became extremely popular, they were able to secure the financial backing required to form a team and produce an actual stand-alone game.