There should be an overhaul on second jobs and outside earnings.
Simplest way to run it would be that unless you're working in a professional qualification such as in the NHS, or maintaining a small family business from before entering politics and that can't be influenced by government policy, then your sole job should be as an MP.
An example of the latter would be someone like John McNally, who had operated a barber's for decades before being elected as an MP.