Salvaging the switches, especially the double slip switches is a cost effective approach. Pulling the 3rd rail would only need to be done in the most visible areas. You may never need to pull the 3rd rail from the switches, especially if there is a chance of damage to the switch operation.
The most important design consideration is to have a hidden staging yard, either under the layout or in the next room (you may need permission to use the next room). In these locations you can use the 3-rail track, as it would not be seen. It is amazing how many engines and rolling stock you want to run that do not "store well" on the layout.
Hidden staging, double slip switches, dead rail conversion & scotch, not necessarily in that order.
