1) Add a part that scans for biomes. Put this very low in the tech tree. Scanning rewards you a small amount of science. 2) Add an interface overlay in map mode that indicates the various biomes on the bodies you have scanned. The Science Archive is nice, but we need a way to know what biomes are out there that we haven't visited yet. The above two would create a more natural and intuitive self directed mission schedule. First you just launch a rocket, maybe get it sub orbital. Use your science to buy the Tier one tech group that has the scanner in it. Send up a ship to scan kerbin. Now that you know what and where the biomes on kerbin are, send suborbital missions to each to collect data and more science. Now send a mission to scan the mun and/or minmus. Follow up by sending missions to each biome. Rinse and repeat for the other planets/moons. You also need the above two for what follows below. Without them any sort of directed mission structure would be either too hard to figure out, or too generic. 3) Add a currency (Kerbucks) to the game and a cost on all parts. Tier 0 and possibly Tier 1 parts should remain free. Those free parts were found lying by the side of a road anyway 4) Earn money for Achievements. Like first ship out of the atmosphere. First Kerbal landed on the Mun, etc. 5) Recovery of ships landed on Kerbin gets you back 90% of the part cost for what you recovered. 6) Add contract missions. These missions would be offered by various companies and government entities. Successfully completing a mission would gain reputation with that company/government entity and unlock more (harder) missions from them. They would be your primary way to earn Kerbucks on an ongoing basis. I envision two main mission types: A) Data Gathering. Things like "go to Near Jool Space and collect 100 mits of data". Notice how I said data instead of science. Even if you have already exhausted the available science in a biome, you should always be able to collect data for missions. If you get a contract for a biome that you haven't scienced out yet, the science earned is just gravy for you. These missions could be generic data gathering, or could get very specific. Like gathering data on mystery goo from Duna's surface and returning the goo to kerbin. They could also be multi-part. You would choose whether you want to complete each requirement with it's own ship, or attempt to satisfy all requirements with just one mission. Some of these missions could require processing in the space lab to take place in the biome in question, effectively requiring that it be a manned mission instead of just probes for everything. Widget Delivery. Introduce a new set of parts in it's own part category. These parts have no inherent function on their own. They are simply cargo of various shapes, sizes, and weights. The point of these missions would be to deliver these widgets to the biome indicated in the contract safe and sound. When you accept a mission you get one of the required widget for free. But if your mission fails, you would have to purchase an additional widget for your next attempt. Some of these widget delivery missions could be multi-part. Like first take this widget to Ike's surface, then take it to near Moho Space, then return it to Kerbin. Some of these widgets could have a lever on them that requires a EVAed Kerbal to pull it. This would effectively dictate that your mission be manned instead of just sending probes for all of these missions. You would always have low reward contracts for missions that are easily doable with the free tier0 + tier1 parts available to complete. This way you never find yourself out of cash with no way to earn more. IMO these things would make career mode a complete experience. They would create a more natural and directed mission progression while still giving you the sandboxy feel of deciding which missions to attempt and giving you complete freedom to decide how to complete them. One of the things that really made the initial release of career mode a great addition for even experienced players was the constraints that moving up through the tech tree imposed on you. Forcing you to attempt a mission with a limited set of parts really brought out a new appreciation for many of the smaller, lower tech parts. But that feel completely goes away once you complete the tech tree. All you have done by playing career mode is earned your way into back into Sandbox mode. By adding a currency and a cost to all parts this would extend that challenge through the end game. All of your designs would have to be efficient. You could still over engineer the crap out of your rockets, but you would need enough money to do so. It would also greatly differentiate Career Mode from Sandbox Mode even in the end-game. Also, in Multiplayer you could have competitive challenge missions wherein only the first player to complete it gets the reward.