Most boilerplate consulting contracts require you to notify clients of subcontracting arrangements, and many BigCo client boilerplates forbid subcontracting altogether.
But so what? You talk to your client about a prospective engagement, then you build a "dream team" proposal that puts you on the hook for the performance of the whole project and makes you the single point of contact for all project matters, but then uses the specialized expertise of partner firms as a sales point. You sell with the subcontracting arrangement, not in spite of it. It's not something you sneak in under the wire.
But so what? You talk to your client about a prospective engagement, then you build a "dream team" proposal that puts you on the hook for the performance of the whole project and makes you the single point of contact for all project matters, but then uses the specialized expertise of partner firms as a sales point. You sell with the subcontracting arrangement, not in spite of it. It's not something you sneak in under the wire.