From my own experience.
In the past 12 months I have witnessed 5 incidents with towbarless tugs. At the same airport with 3 different handling agents and 4 different airlines.
1. Tug tried to establish positive contact with the nose wheels, the aircraft brakes were off and the chocks behind the main gear had been left well clear
. This resulted in the aircraft being shoved rearwards while passengers and cargo were loading. Fortunately no injuries or damage. SOP now changed for the tug crews to check brakes are set before setting up.
2. Steering lockout pin not fitted, Towbarless tug tore the tyres of the wheels.
Don't know whether the over torque warning was inop or ignored. Made a mess though.
3. Wheels slipped through the lifting bars as the nose was lifted breaking the torque link.
4. At least 2 aircraft seen on the taxiway with the nose gear at over 90 degs, tug still attached and a group of dayglo vested chaps standing around scratching their heads.
As for single man operation, don't like it. Unsafe in so many ways especially in the dark.
As the man said, standard hand signal procedure can be adopted if necessary but it's good airmanship to have a chat with the crew first to make sure were all on the same wavelength.
Engine starting is always done with a man on the headset except for one of the airlines I'm involved with. It is an American carrier so I can only assume the FAA have a different view on the rest.
Just my two penn'th
Edited to add...I don't like the flashing of nose taxi lights either. My retina can't take that kind of punishment just as I'm pulling the steering pin and checking the lock pin has been removed. Please don't do it.