I don't know how realistic this is. I'm sure there are a multitude of hidden costs associated with removing signals in the real world. This proposal aims to make the game less frustrating, especially for new players.
The signalling system is very hard to understand and players will frequently make mistakes. Say a player accidentally places a signal one tile too far north. This has already cost them (for example) 2500¢. If the player wishes to move the signal one tile south, the total cost expands to 7500¢ (2500¢ to remove the signal and 2500¢ to place the new one). The player then realises they have made another mistake - they have accidentally placed a permissive block signal, when they intended to place a regular stop signal. Their total cost expands to 12500¢.