We had trouble to achieve and maintain a constant temperature throughout the whole kettle. We also found the filter process inefficient.
We've searched for solutions for these problems.
The first solution was making a RIMS setup. (Recirculating Infusion Mash System)
The second solution was using a BIAB (Brew In A Bag)

We enthusiastically started converting the kettle and unfortunately forgot to take pictures.
We did take pictures of the end result in action and it's working perfectly.

The tap at the bottom of the kettle is modified with an angled tube. 
This ensures the kettle can be drained almost completely (as is visible in this picture)

In the top of the kettle we built a angled tube which secures circulation trough the BIAB.
We also are able to regulate the speed of the flow ttrough the valve.
Next to this valve we've installed a temperature sensor which is connected to the brewpi (for a later project, to control the kettle by the brewpi).
In this phase we can monitor the temperature with the brewpi software and manually adjust the temperature in the kettle.

Final setup; the angled tube connected trough silicon hoses to the pump.