Ghengis,
The more the automation, the greater the COST, the greater the chance of something going wrong, and flexibility of operation is reduced. However, workload and the probability of human error SHOULD be reduced. Just a few thoughts:
1. If you have the facility to select magnetos individually, you can deselect a faulty one and perhaps restore smooth running to an engine that is running roughly due to a mag problem.
2. If an engine has a tendency to overheat at high power settings and low speed, you can reduce CHT by running the engine with a richer mixture. Also, you may be able to squeeze a bit more power out of an engine which is losing power for certain failures by selecting fully rich mixture.
3. If you link MAP and RPM such that you only need one power lever, you will always have low RPM for low MAP. This will increase the time that it takes to achieve full power from idle/low MAP during a go-around/roller landing/stall recovery which could be unacceptable. Also, there are times when you might want max RPM/prop blades on the fine pitch stops at low MAP to give some extra drag and help slow down. And if the prop blades fine off too slowly when increasing power you may overboost the engine.
It is interesting to note that the Merlin engine has far less controls than the Lycomings to which you refer and is simpler to operate! The DB605 in the Bf109G (and similar installations in other German WWII aircraft) had an automatic function for matching RPM and MAP to maintain an optimum relationship, but it could be, and was, operated in a manual mode for take-off and landing. All engines are different and you need to match cost, reliability and operating flexibility and then see what controls are needed. BTW, the Hawk also has switches for the ignition, and electric fuel pump and engine starting, but never let the facts cloud a good arguement!!
Did we ever fly the Hawk together? Best regards. L.