I'm not really sure what you are asking for. From what I understand it sounds like you have multiple people using the same computer, and they all want their own Firefox profile open at the same time. You've got a shortcut for each profile; and it works... but you are unhappy with how the Windows taskbar looks when you have these multiple profiles open at once?
I feel like its a bit of a stretch to blame Firefox for what the Windows taskbar does while you have multiple people simultaneously trying to use the same web-browser. But sure, everyone has their own use-case. And if this isn't doing what you need, then it makes sense to look elsewhere.