In order to help prevent the inevitable "pay-to-win" style of most free-to-play games, we introduced a skill learning mechanism in our current title "Illyriad". Basically, we don't allow any circumvention of research time to learn a new technology, and that acts as our primary braking mechanism - as there is well over a year's worth of research available for each and every city in Ily. If you've played Eve Online, you'll already be familiar with the mechanic at a player account level.
In AoA, we're going to have a similar system, though we're toying with the idea of making each skill:
a) infinitely researchable (but with diminishing returns), and
b) active as well as passive. ie, the skill level you have in a particular thing that you've researched is "banked" and always applies a bonus. This is the "passive" skill bonus (shit that you know how to do). However, if you're also currently working on researching this particular skill further, you get an "active" bonus in addition to the passive bonus (you're even better at this because not only do you know shit, but you're actively focused on it as well). We'd need a mechanism that prevents (or slows) the number of times you can change your "active" research in a given period of time to prevent insta-skill-hopping.
c) We're also considering making many skills specific to a particular ship class or modular grouping. So, for example, an engineering skill that increases base speed might be researchable for the interceptor hull class or for a particular type of engine (eg Ion) as a separate research from something that boosts speed for a Transport hull-type ship or a (eg) Fusion engine.
Any thoughts on these ideas?