"That is a good one!"
It does not make sense. If you say "c'est une bonne" you have to have something else after bonne since it is an adjective. C'est une bonne pomme, poire, voiture, etc. "il est bon celui-ci" would mean He is a good one and not this is a good one. Let me know what you think about that.
You are definitely correct on "C'est une bonne". In fact this phrase can mean "That is a maid/servant". See http://fr.wiktionary.org/wiki/bonne for that. Keep in mind that "il" and "elle" can always refer to "it" based on the gender of the object in question. Generally if there is no gender present, the masculine form "il" is used. Now if we translate "Il est bon celui-là" word for word, it becomes either "he is good, that one" (requires a person present in the context) or "it is good, that one". Though, since we cannot translate word for word for intelligent speech, the second one turns to "that is a good one".