Polyline draw over a leaflet map with custom user defined markers

We need a simple and responsive web frontend with a map where you can define a polyline and markers in there with icons defined by the user (could be from a preselected list of icons). You should also be able to export the model of the map (polyline and markers) in json format to a text file. Finally you should allow loading a model in the same format and display the polyline with the different icons in the map. Ideally we would like it created in React.js but we are open to suggestions. Also with the map, we suggest leaflet ([login to view URL]) but any map that could be rendered in both iOS and Android would be considered. This is a POC (Proof of concept) for a project coming soon, we would like to find a good fit that would be available to be contacted in the future to assist us in the development of the project.