herbreeves,
Thanks for reaching out! You could easily add some custom fields so users could submit this information, however you’d still have to customize the template files and the meta walker to modify the map code to use these custom coordinates instead of the address.
Since this is quite a complex customization, your best bet might be to just add a URL field and allow users to submit the Google Map link themselves. Hopefully that gets you pointed in the right direction, but please let me know if you have further questions. Thanks! 🙂
-Casey-