Well, sure, but you wouldn't use numeric indices to refer to that. :P It might be something like this:
(subset x 'foo 'bar 'qux)
As opposed to:
(x 0 1)
Which would be slice notation, which would work only on ordered sequences, like lists.
Which isn't to say that table subsets would be a bad idea, just that it's a different idea from list slicing, so there shouldn't be any ambiguities with slice notation (which was one of rocketnia's concerns).
You could implement subsetting at function position, in which case it would be ambiguous. I already use :default in wart, so I don't care too much about that :) But yeah I hadn't thought of how to create ranges of keys. This may not be a good idea. You can't distinguish table lookup from a subset table with just one key/val, for example.