You don't need to use 者 with たる; I've seen it followed by a variety of nouns, though they generally refer to a person. AたるB might be a more comprehensive format?
Are たる and ともあろう interchangeable? I've got two questions in my book where たる is the answer to one and ともあろう is the answer to the other. I showed a native speaker who said たる implies respect whereas ともあろう implies disrespect for someone in a high position (similar to まじき?):
1)オリンピック選手（たる）もの、国のためにベスト尽くすべきだ。
2)市長（ともあろう）立場のものが、居酒屋で泥酔するなんて情けない。
Can the kanji 物 also be used for people (as opposed to 者)? The construction section uses 者 but the examples (and some gammer study questions) use 物. Can the kanji 者 and 物 be used interchangeablly?
I was actually curious about this myself, but not having seen anything that describes it explicitly as using one or the other, I split it up depending on what it was referring to.
That being said, I have plans (not sure if it'll happen this year, but we'll see) to greatly improve the grammar linking within sentences, and it'll be much easier for it to bind words that normally have kanji, but hide the kanji depending on the grammar point being used.
