Ear cartilage is an option in secondary nasal surgery if the first procedure has removed all of the usable septum. The septum is the first choice because it is readily available in the nose and an additional site or 'scar' is unnecessary. It can be difficult to judge in revisionary rhinoplasty what is available, and what will be needed to provide shape and support and being prepared ahead for ear cartilage if necessary is a good idea.
Concerning otoplasty, as a routine cartilage in not removed as the ear is folded and shaped by scoring and bending the cartilage within the ear. The scar or incision used in otoplasty is in the fold behind the ear and is very difficult to see. When cartilage is removed for a nasal graft, it should be taken from and area where it will not 'show', in the deep hollow area called the concha. This should not upset the otoplasty result, and as a combined procedure simplifies the issues as the surgeon is already there ( the incision has been made in order to perform the otoplasty and the cartilage to borrow is in plain view). I think that both you and the surgeon will be better off combining the procedures rather that opening the ear twice.
Cost savings may be on the table. It wouldn't hurt to ask.
Best of luck,