I'm a little confused by what you have written so I may not be answering your real question:
The Matlab documentation provides clear instructions on how to use the Matlab engine from C programs. Since Objective-C is just C with knobs on, I see no reason why you shouldn't call the engine from an Objective-C program. All that the Matlab engine will see when it is running are valid calls, it has no clue what language the calling program is written in.
I think that for your usage of mcc is irrelevant; what you need is an Objective-C compiler on your Mac. The Matlab documentation suggests that the compiler included in XCode up to v4.1 is OK for Matlab engine applications. In my experience, it may take a little fiddling with compiler options to make a more recent compiler work with your installation of Matlab, but no more than that.
If you plan to use Objective-C calling Matlab, you may not want to start by writing M-files for your algorithmic core. Actually, you probably will, but the Matlab engine doesn't really run M-files, it executes commands sent to it by an external program, such as your Objective-C program. Your development route might be (1) write M file to implement algorithm, then (2) write Objective-C program calling Matlab engine at critical steps when the Matlab functionality is required. You could write your application to make the engine run an M-file (I think) but this is outside my experience.
While you can use Matlab to run a compiler to build your programs, in this case you are probably better using XCode (or your preferred Mac IDE) to build your programs, taking care to ensure that the right linkages are made to the Matlab engine. Again, the documentation explains what you need to do.
No wrappers are involved. No M-files are required. And good luck getting the Matlab engine running on iOS !