As long as the aftermarket cover can marry properly to the correct gasket, and both can marry properly to the top of the head such that there is no pressure loss or leak, and all hose connections etc. on the cover fits snugly, I don't see how this would cause codes to be thrown, or issues in general. Pressure loss is one of the frequent causes of Vanos solenoid error codes, as correct oil pressure is an important part of their correct functioning.
The problem, of course, now that I think about it, is confirming all of the above before laying out the money for the aftermarket part. To be 100% sure, one would likely have to remove the existing one to be replaced and take it along as a sample to compare with.
Alternatively, one could phone around and speak to a few independent BMW workshops in the hopes that they are familiar with the specific aftermarket part and can provide feedback on whether it worked for them or not. One could also try searching the internet, but specifically for SA spares, I've found that finding information can be challenging, as a number of aftermarket parts distributors in SA are just reselling rebranded ones.