I'm not saying that it should be easy to get it up to 100%,
but with the method you proposed,
it quickly stops adding any likelihood of catching it
unless it was already easy to catch to begin with.
If it's at 10%, it'll go like this:
10 -> 15 -> 17 -> 18 -> 18 -> 18 -> 18 ...
And it'll never go above 18,
even if you throw out another 50 starseeds.
So I feel like the idea of adding a couple % each time
might be a better idea.
It's a slow addition, but if you have a ton of starseeds to throw away,
you'll at least get yourself into "more likely than not" territory
EVENTUALLY.
It'd be more like:
10 -> 12 -> 14 -> 16 -> 18 -> 20 -> 22 -> ... (etc.) ... 50 -> 52 -> etc.
It makes sense that the % would increase over time anyway,
because the Moga should be getting more and more exhausted
from trying to resist that damn starseed anyway, right? ;b