Known issue, which can be fixed with enough DLL work.
An obvious solution, but I am just wondering if that really solves the issue. After all, you still deliver to Europe (or any other market) in integers.
Let's stay with the hunter. He now produces 3.3 furs/turn and delivers 3.3 to the warehouse where they are piling up.
A complete turn for your ship (Harbor > Europe > Harbor) will take 8 game turns.
In this time the hunter has produced 2.4 furs more than initally of which 2 can be loaded.
Or you make it in a way in which even floats can be transported and sold. Buying then would have to happen in non-fractional floats (effectively being the replacement of integers).
But in general I agree that turning as many integers into floats will be very helpful. Especially when it comes to the calculation with pre-known percentual values.
On the other hand that makes the accumulation of percentual values even more powerful.
A fully rebellious city gives you +50%. Full health gives you additional 10%. The respective FF (too lazy to look him up) gives additonal +25%. So now we are at +85% already which are applied to the base production of tile + bonus + specialist.
Maybe the introduction of a cap might be worth thinking about. So that the production of any yield would be limited to 10 max per turn per unit.