Not a good idea, IMO. Why not write or keep it as an external? Changes to the core vocabulary shouldn't be done unless they are done in all versions of Pd.
i see your point ... on the other hand it's not consistent to provide several data structures (floats, symbols, lists ...) and only some of these data structures are being supported by change... imo, a _change_ for different data structures (that might be used to control the environment...) shouldn't differ from a _change_ for floats. especially if one _change_ is an internal, the other _change_ an external...
don't understand me wrong. i don't want to add a new command to the core language, i just think that it would be more consistent, if a command that would make sense for every data type only works for one...
cheers...