that'd be one additional material check when animations are about to be switched...
...a second check for object width, and maybe a third one for object type, or a keyword or something like that that marks an object not/climbable...
so that's 3 additional things to check. so, the problem was... where again...?
tons of other (and far easier and more straightforward) ways to check that (see above for just a couple from the top of my head). definitely no markers necessarily required (and a marker approach is not a method of checking anyway, but a method to work AROUND having to check anything. it's the _opposite_ of checking actually.)