I don't like the idea. The present user might have a specific purpose in mind for the socket, but as it is in a general purpose area (rather than say within an equipment enclosure) other people might use it for anything. A 10A MCB or RCBO won't trip at 13A, it will be in the grey area between In (the rated current) and 1.45xIn (the current at which it must trip.) So no-one will necessarily realise anything is wrong, but the device could routinely be run above In. It falls foul of the requirement Iz>=In<=Ib and is therefore bad design.
OTOH it is more likely to nuisance-trip on inrush too, e.g. a microwave that takes 5A can trip a B10 when you press the start button. Nuisance trips are bad not only because they are a nuisance, but because they make people complacent about resetting circuit breakers. 'Oh, that one always trips, don't worry about it' and don't then associate a trip with an electrical fault.
These are problems that you can foresee and avoid, so IMO you should avoid them. Not having the right device in the van is not justification for poor design.
