What is it you want to see in particular in each city?
The problem in my opinion is trying to deal with all the logistics AND have sufficient time to see what you want to see or even experience anything meaningful.
Early flights are OK but that means getting up very early and getting to the airport 2 hours before your flight. Be aware that Ryanair favours airports that are more provincial than the main city airport and you may find yourself further away from your destination than you expected so that entails longer and more expensive transportation. You could end up finding yourself arriving at your destination late morning or even lunchtime so that's half of one day gone.
Now you have to familiarise yourself with transportation (presuming you'll be using public transport) and a general sense of direction and location. For me, at this time and having been up for so long I'd be thinking about lunch and I mean a decent one, I don't travel abroad only to end up eating a shop bought sandwich, I want to eat well and something regional however I accept that not everyone shares my view.
If using Airbnb be prepared to be at the whim of the owner as to when you can gain access to your accommodation. Sometimes this can only be in the evening if they have work for example, which can be an issue if you have to lug all your baggage with you for a whole day.
By now it's probably mid afternoon and not much has been achieved. Are you planning on two days per location or two nights? If two days you've got the rest of today to see the sights before another very early start to get to the airport for your next flight. This is exhausting and it's a very bad use of your time. You're not actually experiencing the city or seeing much of what it has to offer. Yes you can say you've been there but you haven't really BEEN there.
My advice, pick a couple of cities in close proximity and spend 3 nights in each one.