From: Oxford, United Kingdom
Operating isn`t actually unlimited, it requires units on railroads with enough supply. Maybe the costs are a bit low, compared to Breakthrough; but the system works fine, since not every turn is 7 days long.
What could be fixed is the one-way-railroad connecting over sea straits: the Bosporus, Kattegatt as well as Messina allow operating in only one direction.
I think operational movement is actually pretty expensive in SC WiE, at least until Logistics is researched heavily, but then you deserve some payback for that. In Commander Europe at War GS, each major country could operate up to a certain number of unit points (different types of units had a different operating "weight") for free, different for each country, you could operate over that, but then the costs started to get exponentially more expensive.
I'd actually be in favour of making operational movement cheaper (or even free) for the initial few units operated in a turn, then getting more and more expensive as more are operated.
Regarding the straits - Which (if any) of the straits had a rail bridge at the time connecting the sides of the strait? Those that didn't probably shouldn't allow operating in either direction, those that did should allow both directions.