About innovations in SR2, the whole "import" mechanics, the "diplomacy" mechanics, ship design and ship scaling are things I haven't seen in other space 4X. The different FTL mechanics are pretty nice too.
Well this. Let me explain a bit more then.
Import works like this: a planet has one "produce" which it can export, and a "level" required to export said produce. Raising the level of a planet requires importing some produce. Then, a produce generally generates "pressure". Pressure will automatically build "civil" buildings on planets (you don't have a say what pressure does, only where it goes with imports).
Food for example is lvl 0. Water lvl 0. Electronics require lvl 1, and generates 3 money pressure.
If you import food and water to the electronics planet, it becomes lvl 1, it's population raise, it begins giving tax income (lvl 0 planets cost money), and starts generating money pressure.
Money pressure is some kind of "cap" which determines building built on said planet, so basically 3 money pressure can build 3 markets (require each 1 pressure) or 1 market and 1 bazaar (which requires 2).
If you then export the electronics to another planet (to make a lvl 2, you need 2 food, 1 water and 1 lvl 1 produce), the pressure moves to the planet where it's exported too.
Requirement then increase up to level 5 planets, requiring each 4 lvl 2 planets and 6 lvl 1 planets if I remember well, and 5 food and 1 water. Of course, both lvl 1 and lvl 2 planets also require their import.
As a side note, it's also possible to create "imperial" buildings as you see fit. Civil != not you, empire = you. Those include additional food / water in case you need them.
There are of course some "special" lvl 0 produce which give special effects, and other produces which don't export, but produce "bonus" effects like free FTL, artifacts or bonus influence cards.
It "sounds" complex when writing it but really is easy to understand in-game. It creates linked sprawling empires. Fun part include removing key resources from enemy systems which will crash its economy =).
Diplomacy is card based, not much diplomacy in the "real" sense. It's more a "point" bonus where you vote and create action based on how much influence you get. I'd suggest a let's play to see what it does. You buy cards, which give you special actions (some of which can be opposed) like naming a system (give bonus to attack in it), a flagship, or stealing "peacefully" a system from your opponent.
Ship design is pretty straightforward, basically you "paint" systems and create stations, flagship and support ships, and give them default behaviour. A flagship, planets and stations can be defended by support ships, and you control the flagships. Then, instead of the "frigate" "cruiser" and so on prevalent in other space games, you just scale them, from 1 to whatever you'd like (there are some limitations), and then, if you can build it, it's yours. Depending on the chosen race, you might have different systems to play with there. Since there are only "few" weapons (about a dozen) it's relatively easy to prepare ships before a game and import them when needed. Yes, the game is in real time so it's basically necessary in multiplayer. There is a decent "auto-builder" if necessary.
FTL mechanics are as follow:
- grav drive (standard FTL)
- gate (teleportation between gates)
- fling (launch up to a planet to wherever you want)
- slipstream (temporary 2 way gate to wherever you want)
Not really innovative, but it's a nice change from lanes, gates and standard ftl drive prevalent on most other games. Launching a planet is really fun =).
Note that it's NOT a complete feature list. There are other stuff like mining and building ring worlds, artifacts, tractor beams and other stuff I've barely grazed. You can destroy planets and stars, colonize moons among other things.