I think there is slight confusion here. I have not used xampp but I believe it is just a bundled package which installs some or all of the following:
That's fine - as it does it all for you rather than having to download rpms, build from sources etc.
If you want to install webmin you don't need to reinstall apache or mysql. The current xampp installations stay as they are.
Webmin will allow you to administrate apache or mysql such as changing timeout limits, shutting the processes down, restarting etc. but you don't need to reinstall any current app.
If you can't find any other GUI type control panel then could just create your own control panel webpage with php.
Another alternative is email. You can use procmail to read emails for startup and shutdown codes and correspondingly start / shutdown processes.