Hey there,
i am Michael Lomas, I am an Australian software developer. I have worked for a national Australian Finance company for 6 years, creating, deploying, maintaining and continuing to develop upon their salesforce system.
I read your project and am confident I would be able to create it within a Visualforce page using mainly html and javascript. I would use slds styling, to make the page more responsive (so that it is mobile friendly), whilst still allowing you to stay on salesforce classic without migrating. I am sure you have heard of slds before, but if you havent it is basically like a lightning styling wrapper that i can apply to a single page.
Javscript, Salesforce's Javscript-Remoting and html will give me all the data from the objects and allow me to sort through it (E.G. Filter fields, latitude, longitude, etc), however the only way to display a map on par to say a google map would be to use google maps in our page, this will most likely require us to sort an api key. Whilst I am creating the tool, I can create my own key and use that, however ongoing you would have to create one for your company. I have found code that will allow me to sub in custom marker points within these google maps, so I should be able to make all the markers pretty distinguishable.
I am confident that I would be able to bring your project to completion. Please let me know if you need anything clarified or would like to see examples of my work.
Kindest regards,
Michael Lomas