Aren't you confusing the idea of 'motion to' with that of actual location?
'Motion to' usually has ad + accusative, the exceptions being those in various mnemonics similar to those you quote: cities, towns, small islands, domus, rus and humus (I've never come across focus in such a list, but wouldn't rule it out). Thus, Romam and NOT ad Romam (which means 'near Rome') 'to Rome', and so on. The critical size of the island of Rhodes is questionable, and my guess is that using ad depended entirely on the writer's idea of an island's importance.
The locative simply indicates, as you might expect, place where, a position without the idea of motion to it. It takes its form regularly from a genitive or ablative, according to declension, for which the rules are to be found in any elementary grammar. Romae means 'at Rome'; Athenis, 'at Athens'.
There are a few irregularities to be learnt, such as domi for 'at home' (where domus, the 4th Decl. genitive might have been expected) and militiae, 'in battle' or 'on the battlefield'. Such a list as you ask for would probably be limited to the few exceptions of whatever mnemonic (or maybe aide-memoire?) you choose.
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I'm quite baffled by the responses (below) to this answer. No noun "takes" a locative, but it can certainly can adopt a locative form (e.g. Romae), where appropriate, to indicate a "place where" — including those on Draconis's list. Motion towards a place is quite a different thing, usually indicated by ad (sometimes in) + accusative, but there are exceptions where the preposition is omitted: these are listed in (and are the purpose of) Draconis's mnemonic, and in these cases the preposition, if used, indicates proximity: ad Romam, for instance, means 'near Rome'