I love those ideas! Would make it so much more satisfying.
Well, from a human point of view.
There is some sense to it, but you've got the figures for colonies way too low. It would take a new colony decades, at least, to get the thousands and thousands of cargo ships trading goods. Especially since a colony has to get pretty big before any meaningful amount of trade takes place, and all the colony ships coming in would reduce the economy to about -150% before things got going. And you'd keep getting colony ships coming even after the colony was fairly established, hurting the economy far faster than it could recover. So, millennia before you started seeing any income, probably. If this is going to work at all, it needs some big changes.
Drop the "new colonists hurt the economy" thing entirely. Say that richer colonies attract richer immigrants, or whatever.
Increase the effect of trading at least tenfold.
Add other causes of economic growth. Financial complexes should do the job, of course, and low unemployment should help. It should probably just happen naturally over time, as well, although this should be pretty slow. On the flipside, it would be quite reasonable if things like bombardment and unrest knocked things back a few points.
Most of all, it needs to be nonlinear. It should be pretty fast and easy to get from 10% to 50%, harder to get to 75%, and quite tricky to get over 100%. It should probably constantly degrade to 100% if it's higher.