GA4 is a lot more powerful than Plausible, plus we charge per site and not page views. If you want to self host than yes you can choose whatever OS tool you want.
Yeah, but why use the more powerful GA4 if you want a simple dashboard like Plausible?
Another concern with GA4 is that visitors data goes to Google – not good if you have privacy-minded customers. (Naturally, this shouldn't be a problem in your case as you market to those already using GA4.)
Could be that more than one person in the company uses GA4. One team might just need the basic stuff in a simple dashboard. Other teams might need the more detailed data you get from standard GA4.
Another concern with GA4 is that visitors data goes to Google – not good if you have privacy-minded customers. (Naturally, this shouldn't be a problem in your case as you market to those already using GA4.)