> I'm not quite sure what you mean here. Are you talking about undue importance given to small parties in such systems?
No. The proportional list system prevents representativeness. The people whose name is on the list represent the one that put them on it. They do not represent the electors.
> Separation of powers: not happening in Spain. The most voted political party in the legislative elections forms government.
> That's not how separation of power works...
Exactly. I was explaining what happens in Spain.
> Imperative mandate: Sieyes abolished it during the French Revolution and it still to be restored in all Europe. The elected candidates in the legislative elections should remain loyal to their promises.
> I'm also not sure what you mean by "imperative mandate". As for promises... well, there are promises and there is political expediency.
The electors should have a contract with their representative and if they are not loyal to that contract they can be ceased.
> Different elections: for executive and legislative (like in France)
> I'm stopping you right here. It makes very little difference in practice, since the elections for the lower chamber happen right after the presidential elections. I also don't see how it's a benefit in general. It suffers from the idiotic, anti-democratic first-past-the-post system. I'd rather have a token President and a PM coming from a coalition instead.
It makes sense if you think about the different characteristics that you look for in a legislator in contrast to the values required to be a president. A legislator should be loyal to their representatives (a part) whereas what you are looking in a governor is intelligence to guide the Nation (all). It is nonsense to think that a good legislator could be a good PM (UK). Loyalty vs intelligence, that's why it should be different elections.