Not a bad idea, as such.
I mean, if the idea is to explore cleverness is using youyour language as choice, then so knidkind of handicap is clearly necessary.
And given the number of challenges that have "read input" and "write to console" parts, this metric has some validity, but it surely doesn't tell the whole story. I mean various languages I use could be accused of having various advantages and handicaps:
awkdoesn't require anything to echo the input, but has underpowered associative arrays and needs an unnatural approach to do non-trivil stuff to more than one input file at a timechas no sophisticated data structures built in, and a B&D type systemc++has a better standard library, but it comes with wordy type names and still has that sex dungeon feelfortran 77has implicit type, built-in complex numbers and inline for loops in in-out-put statements, but has column requirements, lengthy keywords, and no data structures more complicated than an array.
so the degree of handicap depends in a non-trivial way on the problem posed.
Trying to set a single metric is asking for endless arguments which can only be settled by "This is the official word on the subject, so shut up already."
My "solution" has always been to vote for cleverness as well as shortness. That's not objective, and not fair insofar as I can only detect cleverness in language I comprehend, but it's better than nothing.