Windows: Only works in specific applications. Chrome it works, Microsoft Office suite is doesn't work.

Ctrl-Alt-V for Office and its ilk. My tip is to always set to paste without formatting by default, and use the shortcut when you want to paste with formatting, because the fancy format you want is usually pre-selected on the menu, but the plain text format never is.

I use the Option+Shift+Command+V all the time, especially in emails - that text that I copied from SAP or a Word doc invariably has bizarre formatting and if I Command+V paste it into my email, now the rest of what I type after it is going to be screwed up. A four button shortcut sounds like a pain, but once you use it two or three times it comes pretty naturally. Similar to Command+Control+Shift+4 for setting up a screenshot that will grab straight to clipboard, it's easier than it sounds when doing it on the regular.

I wish email clients would ignore font and font size, but maybe not bold & italics of content pasted into the middle of an existing paragraph.

But keep almost all formatting (except font size) if pasted into a new empty paragraph.

But under no circumstances have the formatting under the cursor after the operation changed.

I know that breaks all convention and would probably cause more problems, but boy would I be happy.

Yeah - seems like it would be one of those things that you could allow the user to configure and they'd set it once and never again. I suppose you could switch your client to plaintext composition, but would be nice if there was a setting like you describe "don't change formatting after pasting" and/or "always strip formatting when pasting".