Thank you for your proposal.
Indeed, previously, this was exactly the way in which we had declared the fullname (this was a smart field and the same mechanism for the search).
It was working, yes.
However, because of performance problems linked to the use of smart fields (performance issue and performance issue #1008), I have decided to move multiple smart fields definitions to native SQL fields.
As you can see, I already made many many different tries in order to solve all my issues.
The things improve little by little, but I would prefer to keep my current setup.
Your solution would be a good workaround if there were no other problem (and restrictions) with the use of smart fields, but this is not the case yet.
And we should definitively have a way to serialize the data without generating other issues. I think that it could be fixed quickly indeed.
Thanks for your help.