Multiplayer Turn-based RPG Grid Platform

What I’m looking to create is a platform where a host (game master for role-playing games) can load a grid map and elements they control (like monsters or traps) and they can insert characters that other players are controlling. The host should be able to control the game elements they load, as well as modify or override controls of the other players. The players should be able to make character selections from a template, and then control where those characters move on the map and what action to take on their turn. (Spell, attack, etc.) Map movement and action range should be limited to standard parameters, and adjustments the host selects. (“Players can move six spaces normally, but host can change it to 3 for this swamp map.” “Legal targets for X spell can be up to 4 spaces away.”) The important thing is that assets can be loaded, standard rules can be defined that limit player control, and rules can be overruled by the host. Is something like this possible? If so, what would it cost to develop?