Handling NRT in Scenario Editor (SE)

Which RoadTypes should be available to be built?
 - Tramways are buildable only by players (not city)
 - Some RoadTypes could not meet the requirements for a fair play
   - May allow only a particular vehicle category to travel on them, in SE one could not know it
   - Future roads with house-unfriendly flag used as town roads will make the city disappear when playing
 - Date-introduced RoadTypes will be always available, like industries
 - Owner none?

Features which could be useful on SE
 - Convert road tool
   - Works regardless of RoadType compatibility?