Add an instance to a virtual subclass?

With abstract subclasses on can use register to add other classes as a "virtual" subclass, what would be a way to do that for a single instance based on it fullfilling some criteria?

The "sensible" alternative I came up with is using virtual subclassing but changing the instance check dunder method

class Controller:
    def __init__(self,smart)
    pass

class SmartController(ABC):
    def __instancecheck__(self)
        return self.smart
    

but this didn't work since Controllers metaclass actually has to have an altered instance_check for this to work, which makes me think you might have to do something with metaclasses, but if Controller allready has some other metaclass I don't know if it would work...

possible reason for doing this: Controller might have some childclasses which the individual instances can either be "smart" or "stupid"

I realize this might be a very bad thing to do but if there is some "most sensible" way to do it then I would like to know how

Also would like to know why this is actually a bad idea if it is one