It doesn't sound very natural, and I agree with Chris that it's a bit confusing. You might say, "After the week I've had, I could go for a post-lunch iced coffee!"

Jack said that Tom was waiting for the bus when Harry arrived. There isn't just one right way to say this.

It’s perfectly natural in speech but would be clearer written with ‘post-lunch’ . In speech we would pronounce it so that ‘post lunch’ is obviously an adjective of time modifying ‘iced coffee’. Saying “something ‘calls for’ something” is a phrasal verb meaning ‘requires’. That good news calls for a celebration. Telling her some bad news calls for some tact. Etc

I kind of agree with the others, but if there was enough context before this sentence (e.g. we already know that Wednesday is your Friday), and if it's your style, it might be fine. Also, if we want to be really technical, I believe compound adjectives should be hyphenated, i.e. 'post-lunch iced coffee'.

Not really. Not only is not "natural" but it is very confusing. I'm not sure what you are trying to communicate. Do you want to try and explain with more words or in a more formal style?