I severely doubt that the Allies would have attempted such risky operations. The problems with either (or both) are many.

First, the Venice proposal requires moving a fleet into the very restricted Adriadic Sea unsupported by air power (beyond whatever carrier aircraft might be provided. It is a long and exposed sea route that would have given the Germans and Italians considerable time to apply both sea and air power to attack the invasion convoys.

The Monaco version would have required the conquest of Corsica and Sardinia first to avoid having Axis forces and air power in the rear of the Allied landings. These islands would also be required for the Allies to base their own air power for support.

Both landings expose the Allied supply train to attack. Both would have long and very vulnerable sea routes of supply. It would be akin the Rommel's problem with Malta in North Africa.

Dual landings would not be possible given the amount of amphibious equipment the Allies had available.

This does not even cover the problems in politics that either would face, particularly from the British.