Some pointers to anyone thinking of re-writing the constitution:
1) Don't make the President's job too important. It should be basically ceremonial, with the exception of a few tightly-defined reserve powers designed to get the country out of constitutional crises (e.g. the power to dissolve parliament if it fails to pass a budget). By making the job ceremonial, the separation of powers becomes much clearer - executive power rests solely with the Prime Minister and his / her government.
2) Don't give the job to a politician. Define a group of candidates who are "worthy" by virtue of either the role they hold (e.g. chief justice, national bank president, ambassador etc.) or by the titles they hold (e.g. order of the republic*). Candidates must not have been party members or have held a politically appointed position for five years. They must also agree to their nomination.
3) Organise the election in such a way that there must be an outcome and that the candidate enjoys broad support. Put the candidate group past a parliamentary review committee where they need to receive a 2/3 vote in order to make it onto the short list. Put the short-list to the vote in a plenary session of Parliament. Successively eliminate the lowest polling candidate until there is only one left.
The end result - (a) no constitutional drama, (b) clear roles and responsibilities and (c) a half-decent President.
*The procedure by which such orders are obtained will be topic matter for another post....