Hmm. So I get what you're saying, but does this really hold up?
An experienced player isn't going to wait around for the stipend to tick while doing analyze missions - not because it isn't fun, but because they can ramp up way, way, way faster by using those analyze missions as starting points for salvage expeditions. Or by doing something else (bounty hunting etc) to get going.
So, yeah, technically it's reward with no risk, but it really just acts as a mitigator for the calculated risks you can take while it's ticking. This covers "analyze" missions, too; grinding them is slower than the alternative, even if you factor in the risks not paying off sometimes.
For a less experienced player, they're not going to have "how to get to endgame in an easy, slow, and boring way" mapped out (due to being inexperienced), so again, this stuff ought to act as a mitigator, analyze missions will naturally lead them into salvaging ("hey, what's that other sensor contact nearby?"), and so on.
I feel like "all reward and no risk" is indeed dangerous, but primarily if it's not passive. Then the player may feel forced to do it instead of doing more interesting, higher risk/reward activities. When it's passive - and comparatively minor, to boot - it's just a backdrop to other stuff they'll be doing.
I do like the idea of blockades. Ideally, the player would also be able to do them, though, which right now wouldn't be possible. Even so, it'd be a nice change of pace from expeditions - I don't think I'd want to replace expeditions with these, but adding them into the mix could be good, provided the possible ways of dealing with them were solid.
(And, yeah, colony income needs nerfbat, since it does trivialize everything else.)