The client says that I am allowed to direct each of the teams on what they must do to achieve the integration goal, and they must accept my direction. The client is also fine with me billing hourly, so I'm not worried about getting squeezed on a flat fee. But I am a bit lost on how to define liability. The client, understandably, wants me to accept some liability. But they are looking to me for guidance on this.
Had anyone else dealt with this? How did you define the liability?
You are being asked to accept liability for people without an incentive to deliver good work of whose reputation you don't know.
The more unspecified the liability and acceptance/delivery or services description is, the more likely you are to end up with an endlessly "unhappy" client who won't make more payments but won't say it's all finished.
I suggest you run. Never take liability without responsibility, especially not without any large upside possibility. In the absence of clarity, clients will try and argue that you own the liability because you directed other people for the final product. You want to specify details and work against them with a healthy 20% buffer of extra quality/work to make sure the client can never argue you didn't fufil the work. This is the opposite of that. Don't do it.
So you are already in a good place - hourly rates, define and communicate the specs to the other devs, and reject liability. If the client says no to that, walk away.
IANAL but my understanding is that for contractual work in the US you can only realistically be sued for at most the amount of the contract (supposing non-negligence). Asking you to accept liability beyond this sounds risky.
That said, the way you've described this, it sounds like a disaster waiting to happen. Either this client really doesn't know what they're doing, or they're holding a hot potato and hoping you'll take it from them before they get burned.
2. Middle-ware can be expensive or impossible depending on the paradigms deployed
3. People that outsource with data-mining talent are usually as unreliable as they appear
Usually trust your instincts as they often warn you somethings off... =3