I"m going to assume that "like" means "yes." In that case, I concur with Chris and then some. The last Class I/II device company (not contract manufacturer) I saw try to take on Class IIIs...let's just say that did not have a happy ending.
It didn't seem to be the typical "they just won't listen," after numerous people tried to tell them, but that companies that have long experience with Class I/II simply have a hard time wrapping their minds around Class III, even if they want to. It can seem like you are dealing with a whole different FDA. Much more scrutiny, much less flexibility, much quicker to move to enforcement action.
If you were a device company, I'd advise you against it. However, if your responsibilities are limited to manufacturing, I will say tread with extreme caution. In particular, I would be very clear on the responsibilities you are inherently taking on under the QSR, and which ones you are agreeing to take on in your agreement with your client.
If you've been in this biz for more than 5 minutes, I'm sure you won't be shocked to hear that device companies, especially startups, frequently try to task out their legal responsibilities along with the contract work. In some cases, that just doesn't work, because the QSR is clear. In other cases, there can be some gray areas where the contract manufacturer can find itself on a hook it didn't know was there. Complaint management and investigation is an area I'd look very carefully at, along with responsibilities related to management review. And I'd make sure your client knows whatever you know, as soon as you know it.