Fleet points from planets was done for a while in beta, with various planets offering different amount of fleet points as planetary upgrades. But that had the potential to skew balance quite a lot and make it so an unlucky random map player would never be able to match the fleet numbers of an enemy. It also creates too big of a slippery slope if only a few planets are lost.

This is what I would propose about fleet supply:

I think in additional to the ship's building costs, add a fee for each ship your have

Not so much that it will tax your income away but just enough so you get a modest income.

You don't have to like it, I am just putting my 2 cents

or reduce the number of fleet supply it cost

Well, I'd happily welcome a change in the way fleet logistics work - I really like the idea of each ship having a certain upkeeping cost - though it'd have to be rather low.

Why change the system?

Now, sometimes one builds up a large fleet to, say, fend off an invasion or expand quickly, but after this is done, there is no way to undo what has been done, i.e. bringing to upkeep cost to higher levels.

It'd be nice if losing or scuttling ships'd actually have an impact here.

It all comes down to flexability.