I'm not even sure if career mode is going to happen, but if it is, here's what I personally NEED in there; realistic spaceflight contracts and busyness model.
You already may be aware of another space program game, which already has a career mode. That career mode, however, is not at all realistic. Well, to be fair to it, when it came out there weren't really any spaceflight companies that weren't state-owned or heavily funded, and we all agree that a government funding simulator wouldn't be much fun.
But now, there is finally a company that is playing real world career mode; SpaceX. And I think that the busyness model of SpaceX (and all other commercial spaceflight providers) should be reflected in SR2's own career mode.
First off, I suggest taking a different approach than the competition. There should be a design freeze feature that would let you make some of your saved rocket designs frozen, so that you could not alter them at all, with the only possible modification being attaching parts to interstages and changing shapes of fairings (to allow for differing payloads). When you launch a rocket (design of which is frozen), you get a slight discount for the next launch of the same design. This way, as you keep re-using the same rocket, the launch cost will go down, simulating an improving manufacturing process, just like IRL.
If you want to modify a frozen design, you'd have to make a new version of it. That version would lose its launch discount, and to get the price down for the new rocket you'd have to use it a few times again.
This would encourage players to use rockets they themselves are familiar with, improve their skills with those designs, and focus more on the actual game-play aspect of SR2.
Another feature that would be nice to have is when a rocket (or any part) is recovered, the sum value of the parts would be transferred back to your account, but I am sure that is already planned so I won't describe it much.
I'll just say it; KSP's satellite contracts are crap. They are all the same, requiring you to place a thermometer or something somewhere, keep it in there for 10 seconds, and boom you're done. There is literally no use in KSP for satellites, besides a few comsats that are enough to provide coverage to the entire solar system.
I think it would be easy to implement an astronomically (get it?) better satellite system into SR2. I have seen that there is a way in SR2 to merge multiple parts into a single part. While right now it's undeveloped and hidden from the world, I think it could be very well used for satellite contracts.
This is how I imagine a satellite contract in SR2 looking like:
Mission type: primary or ride-share
Spacecraft: the actual satellite to be launched
Destination: the orbit the satellite is aimed for
Duration: how long the satellite has to stay there
Reward: cash money yay
I'll now explain in more detail. I promise that it is simple in nature, it is just hard to describe in a forum post. The mission type is what dictates the majority of the mission. Initially, only primary missions would be available. As soon as you accept one of them, there would be a chance for a few (or many) ride-share contracts to pop up.
The primary contract would be the one dictating the actual destination, while the ride-shares would simply copy the primary destination, while allowing for much more deviance from the target orbit than the primary payload.
Unlike in KSP, where you can just put a single science instrument on just about anything, in SR2 you'd be provided with the actual spacecraft, in a form of a subassembly that could not be in any way tampered with, only connected to an interstage. This is where the part merging I talked about comes into play. There could be a set of pre-made spacecraft in the game that would act in the designer as if they were a single part. This way, new designs could be created, shared, and used by the players. Normally, I'd imagine the primary spacecraft to be a somewhat large satellite, while the ride-shares could be small, like cubesats or something. If a reputation system is implemented, the ride-shares would provide you with a better reputation reward than the primaries, but also much less money.
The destination would depend on the difficulty you've selected, or on the the difficulty of the contract itself. You could have a simple "orbit around Smearth" goal that would be easy to achieve, or something more difficult where you actually have to aim for a correct apogee, perigee, inclination and direction. The more difficult to reach the destination would be, the better reward you'd get from the contract.
The duration would dictate for how long the satellite has to stay in the orbit. While you would get the reward as soon as the satellite reaches its destination, you would still face a large penalty should something cause the satellite to leave its orbit before the mission duration runs out. As soon as the duration runs out, the satellite's mission ends and you are free to do whatever you want with it. The mission durations would vary, but I imagine that they would go up together with the difficulty of the destination orbit, so just like IRL, life of LEO satellites would be much shorter than the life geostationary ones. When the satellite's life ends, there would be no way to control it (without an external force) and it would automatically be marked as debris.
And I think that's it from me. Remember that I don't want the game to be just about satellite contracts, not at all. I just want the part of the game that includes launching satellites to be as enjoyable as possible, not just vague and monotone like in the other game.
All your thoughts regarding my suggestions are welcome in the comments.