I'm not a fan of this new system, but this definitely isn't cheating, in fact it can't possibly be cheating as:
1. The FIA were fully informed of Mercedes intention to run this system, were completely kept in the loop during it's development, and have given it their blessing, although probably reluctantly seeing as it's now outlawed next year.
2. Mercedes have now demonstrated the system to the world before the season is even underway, and have been clear about what the system does - although not the intent of it. This now allows other teams to either petition the FIA to get it banned, develop their own variation of the system - which honestly should be a relatively simple task for any competent F1 engineer, or decide that the difference it would make would not bring anything to the table.
Everything about this has been done completely above board, both with respect to both the FIA and the other teams. I'm also sure that Mercedes have developed this in such a way that the steering system can easily be converted to standard should it be banned later down the line.
Basically what Mercedes have done is said "Hey, we want to use this system, so complain now if you don't like it". Which is fair I think.
