Quite frankly, it's the developer's job to say, "This isn't possible." It's the developer's job to know where the cutting edge is, and to take the time to think about whether or not a completely new design idea ends up being possible to implement after all. If you force the designer to take on this role, it reduces the developer to a code monkey--your job is to ensure robustness--and forces the designer to take on two roles.
I tell my designers to ask for magic and to accept it when I say I can't do this. Their job is to know what affordances are standard and why things ought to be shaped one way or another. That's their area of expertise. My area of expertise is to look at something crazy and go, "Hm, but if I did this then maybe it would work after all."
And when the best way ends up being technically difficult or impossible, we compromise.
Quite frankly, it's the developer's job to say, "This isn't possible." It's the developer's job to know where the cutting edge is, and to take the time to think about whether or not a completely new design idea ends up being possible to implement after all. If you force the designer to take on this role, it reduces the developer to a code monkey--your job is to ensure robustness--and forces the designer to take on two roles.
I tell my designers to ask for magic and to accept it when I say I can't do this. Their job is to know what affordances are standard and why things ought to be shaped one way or another. That's their area of expertise. My area of expertise is to look at something crazy and go, "Hm, but if I did this then maybe it would work after all."
And when the best way ends up being technically difficult or impossible, we compromise.