Relative to the last point, the issue--at least, the issue as it appeared to me--was whether anything special that isn't offered to any other person who has been in cabinet is being offered in this case. When a person gets an opportunity to be a minister, something special has happened to the person's life and career in every case, but we don't consider it a conflict of interest, simply because it's part of the package that is offered to everyone and therefore is not any kind of special inducement. It's only if the inducement is unusual in a particularly egregious way that you would want to say it was therefore a breach of the code.
Relative to the first part of that question, I think it's important to understand that when you're dealing with ethical issues in which conflict of interest is a subset--ethics is a much bigger question than conflict of interest--values almost always collide. Otherwise we wouldn't be discussing this year after year after year. Therefore, it becomes very context dependent. It depends a lot on the particular circumstances of a particular case; making general rules about this is very difficult.