Imitation is the highest form of praise
The Europeans would show good sense if they sent an MER clone to Mars. They'd be capitalizing on our poor judgement for not cloning MER ourselves and sending more copies to Mars. As dtb suggested, if the system was rational, we'd offer to build several uninstrumented MER clones for the Europeans. The Europeans could then instrument the MERs as they pleased and then send them to Mars under a single fairing on an Arianne V or a Proton.
Too bad the system isn't rational.
Gary