The problem with multiple values being subsequent accesses is it would also interfere with a useful syntax (not actually in Arc, but I mean insofar as deciding which it should mean), and that's subsequence indexing. It's been discussed all over the place, e.g. http://arclanguage.org/item?id=449
With the assumption that one of them takes that syntax, what should be used for the other? How about (seq '(0 3 ...)) or (seq (0 3 ...))? It would similarly be fitting for any number of arguments, be they dimensions or indices, though I would vouch to use the list for n-dimensional indexing as the case of subsequences seems more common. Plus the use of a list distinguishes the one type of access from the other without having to go (...((seq 0) 3) ...).
Not that any of this helps your problem. Just something I noticed.
