Forget about servers running melee-only or flat rate run speed. You should design your deathrun maps for normal class weapons, run speeds and health. That way it will work well in all server environments. Test your map as a Heavy, Pyro and Scout to make sure distances can be jumped across, and employ slowing-down measures for fast classes, like obstacles, static hazards and so on.
You can set up a TF2 server on your computer and install SourceMod and a deathrun plugin to simulate the environment and have the team switching but you don't really need it.
Remember that at the start of the map the most players will be alive so don't build narrow traps designed for one player at a time there, or you'll make it very cramped and will kill a lot of people unfairly. Start with easy traps designed for multiple players and end with hard traps designed for single players.