Purely from economics view, what you propose initially seems like a good, less costly, alternative. Even though personally I find the 11€/ month a fair trade, I find the idea of lowering the bar for users who want to be involved less consistently very good. I believe though, that in the long run route pricing will eventually turn the game more expensive if you consider the huge number of established routes currently existing worldwide.
As a simple base case, a user who pays the monthly subscription for a year(currently the most expensive options) it will give (11€ Χ 12) 132€ per year and he is granted access to fly any route and region he wants. If we assume that this user flies on average 300 different routes per year (less than one unique route per day) then the cost for each different route is at 0.44€, less than half of the price you proposed and with the benefit that the user flies wherever he decided on spot and he doesn’t have to plan his route purchases beforehand. This price is even lower for people with 6-month or yearly subscriptions.
It would make more sense to me that another time package will be added (daily /weekly pass) with a lower price (e.g. weekly for 4€) rather than focusing on pricing a huge amount of routes worldwide (which is a time hungry task). This will lower the economic bar for someone who wants to invest less time on the app while it will keep offering the same product and experience to everyone.