Right now Kartographer embeds Mapbox.js, which is Mapbox's version of Leaflet. There's nothing which can't be done with base Leaflet.
We should switch to base Leaflet, which will help maintenance by having us use a more standard library that more people are familiar with. It would also make it easier to keep up to date and get bugfixes from Leaflet.
This has been discussed a fair amount informally and is considered desirable.