First, some background. My question is kind of an extension of this previously-answered question about the difference between は and が. While I am fairly clear on the different usages of は as a contrastive marker or a thematic marker, the explanation given on the page linked above included an example of this sentence used by Susumu Kuno
in which the わたくしが知っている人（は） could be translated to something either along the lines of 'As for the people I know (they didn't come to the party)' or 'People I know didn't come to the party (but people I don't know did)'. Which translation is correct would depend on whether the は is used as a thematic marker (to refer back to people who were previously-mentioned), or whether it is used as a contrastive sentence (that doesn't directly refer to people who may have previously been mentioned).
Here's the main question: assuming that a sentence was used in the context of a conversation where は could be taken either way, such as a conversation containing the sentence above, how would a native Japanese speaker rephrase such a sentence so that the meaning of the phrase modified by は (e.g. 私が知っている人) is more obvious? This is a two-pronged question, since は would have to be rephrased differently depending on which of the two meanings was intended in this hypothetical situation.
My guess would be to use something like としては instead of は to rephrase a sentence if the phrase was meant to be contrastive, and maybe といえば instead of は if the phrase was thematic and referring to something previously mentioned. Whether those would be in any way correct or not, I am not sure what kind of rephrasing would be most 'natural' or 'elegant', so to speak.