Tegola is a vector tile generator, so this would be a vector tileset of OSM data alongside the OHM tileset. The OpenStreetMap Foundation began developing an official vector tileset of OSM data last year. Like the official OHM tileset, it picks up the latest changesets within minutes. It uses Tilemaker instead of Tegola, but the resulting tiles are compatible with the same client-side renderers. This tileset soft-launched earlier this month; check out the demo.
The new OpenRailwayMap shows that a mashup of OSM and OHM data does help users easily cross-reference the past and present. I created a simple demonstration of something similar but based on OSM’s vector tileset instead of a legacy raster tileset. In principle, a mashup could show so much more of history beyond railways.
Integrating a mashup into the main site would help users orient themselves on the map without forcing them to flipping back to openstreetmap.org as often. But this would only be for visualization purposes, primarily for end users. It wouldn’t quite be a substitute for mapping things that extend into the present directly in OHM.