As an alternative to either a bridge or extending the tunnel, how about a gallery? With a mountain there, you could have slides, so roof the lower track over, similar to a snowshed, but with a flat roof. The upper track would cross a reinforced section of it, the roof would keep falling rocks off the tracks below, and the front could be open, allowing the trains to be seen between the support pillars.
Put some loose rocks and dirt on the roof, add an end loader tractor, and you have a scene that can double as an "industry". Every now and then haul a hopper or GS gon up to remove the accumulated debris.
