First of all you don't need a tiller to safely land an aircraft and stop it on the runway...
In my airline we don't have tillers on the RH seat, however when the FO is the flying pilot he will land the aircraft and slow it down to taxi speed. At that moment the captain will take over control and use the tiller to exit the runway and taxi to the gate.
So if the capt. would be incapacitated the FO can safely land the aircraft but he will have to either stop the aircraft on the runway and request for towing equipment, or if the runway has a high speed exit, he could be able to use the rudder nosewheel steering and exit the runway.
@Superpilot In my opinion this policy where the FO never slows the aircraft to taxi speed is not very safe. Is this in the SOPs or is this a habit of the captains to say 'I have control' too early?