Personally, I believe we should have an objective external forum that would make decisions on consequences for those who break the rules. In the case of MPs, due to the division of powers, only the House of Commons can punish an MP.
The Conflict of Interest and Ethics Commissioner can recommend penalties. I haven't had to recommend severe penalties, beyond apologies, and so on. I think that's sufficient, and anyway, it can't be changed for constitutional reasons.
With respect to holders of public office, I send a report to the Prime Minister, and the Prime Minister decides what to do with it. In the four and a half years that I've been in office, I haven't heard directly of any consequences arising from the reports I've submitted.