"Else" can be an adjective or adverb, we can agree. But would it be improper to recognize certain usages as being an indefinite noun, or as a compound noun as in "somewhere" (both an adverb and a noun) as it relates to "somewhere else"? Both are indefinite places, only "somewhere else" is an indefinite place other than the indefinite place referred to as "somewhere". Is one of those more definite than the other? A mathematician using logic and set theory might give a different answer than a grammarian. But either way it seems like a trivial question of no substantive import.
Maybe we can accept variations of syntax and spelling as having a preferred status (according to the source) without the requirement that one form be labeled incorrect from a literary or scholarly perspective. Sure makes life a little easier and less contentious, unless one is obsessively compelled to accept only black-and-white, all-or-nothing single versions, which gets really complicated since most words have more than one definition. The bottom line is whether the message is easily understood by all or most readers, (and whether there are any penalties or adverse consequences which an administrative authority may impose). And if it has the additional factors of consistency and commonly accepted versions, so much the better. Eventually, most languages undergo changes in some way or else another. (I refuse to even try to analyze that usage.)