I've always wondered about tabletop games where the heroes are actually constructive forces. Normally, heroes are surgeons. They help by murdering large numbers of unhelpful things. They help by destroying. Well, at least surgeons stitch you up afterwards - so heroes are not even that nice.
Many of the games I've run featured the players in constructive roles as well. For example, having to build a base in addition to simply killing orcs, or having to make major policy decisions since they are considered arbiters of the Jedi order or whatever. It's fun to create, to alter without destroying. Here are some of the things I've learned and want to try more of.
1) Classic means of determining alignment mean very different things in a game where construction, socializing, and policy are major elements. Even if the game still features a lot of combat, the whole alignment scaffold is based entirely around the idea of fire-and-forget activities.
You need to expand that to focus on ongoing tasks instead. For example, you might have an architect alignment, where the hero wants to build the solution. Or a leader alignment, where the hero wants to guide the solution but has better things to do with his time than get his hands dirty. There are many ways to do this, and some systems have done some things along these lines, but it's good to make it explicit and focused on the game world you're creating.
You can go without this kind of scaffold, but the reason I call it a scaffold is because it is one. It gives the players something to stand on until they build their presence in the world. So I am generally in favor of some kind of alignment/personality scaffold.
2) Balance between classes and characters can get difficult. Characters that are better at different kinds of challenges mean you tend to have one or two active players and the rest are sitting on their asses. That's not a good way to run a tabletop - it's the Shadowrun Difficulty.
You have to build your world such that the constructive challenges work in much the same way as combat. That is, there are many roles, but everyone is always engaged. You can even borrow the framework completely if you're feeling uncreative, just port it over wholesale.
Some people might instinctively back away from this kind of rule scaffold, thinking it limits the player's options. However, it serves the same purpose as a combat resolution mechanic does.It's no limit on role playing things, it's just a way to rapidly and interestingly deploy against varied challenges in the same way as when you would decide to take on those orcs.
3) Constructive play gets world-heavy. You end up with huge amounts of stuff accomplished. In an ordinary tabletop RPG, only a tiny fraction of the people you interact with ever come up again. In fact, you end up killing most of them, if you include monsters as people. But in a constructive game, you're actively building things, and that means you get more and more people, places, and history building up.
To keep this light and fun, you need a system for recording and referencing the world-building. I usually used cue cards with the character (or thing) drawn on one side and notes taken on the other. That works relatively well.
It means a lot when someone your players helped shows up to help them, or even if player character downtime is spent hanging out with people you rescued. Players can really get a feel for the fact that they helped build this world. They really feel heroic, on a level that +500 XP and a cache of gold doesn't convey.