The problem with ice on the outer tank upper surface is easily solved. In fact the Outer Tk's should be empty at landing as an Outer -> Inner Xfer should be done when RTD (Remaining Time to Desitination) reaches 30 mins. If not you can empty the outers with a MAN Outer -> Inner Xfer on ground.
The problem on the inner wing is caused by fuel in the collector cell - which is kept full whatever the fuel load. Each collector holds a bit less than 1 tonne. So even when you refuel the new warmer fuel will not mix with the cold fuel in the collector cell. Switching the engine feed pumps on will help, but not solve the problem.