At the current state of affairs the two main Lebanese coalitions are, not surprisingly, at opposite ends of another issue. The 14 of March parties are advocating electing General Suleiman as President immediately without any conditions or pre-agreement. Meanwhile, the opposition wants to agree on each and every political issue that divide the two coalitions.
The opposition argument is based on the their fear that the next President will suffer a similar fate to the infamous Emil Lahoud, who was practically shunned and isolated by the whole world and did not have a say on policy making. the argument sounds valid, however the timing is quite suspicious!
So why is Hezbollah forcefully postponing the presidential election, insisting on a political agreement with guaranties on all issue, and especially on the formation of the next government, even though once Suleiman will be elected he will still have a lot of influence on the formation of the new government as he co-signs the decree to from it. So if he is not happy with the proposed division of the number of ministers between the two coalitions, or the distribution of ministries, he can simply refuse to sign and all parties will have to keep on negotiating to reach a better deal.
The answer to that question has several facets: first Hezballah and Aoun do not completely trust General Suleiman, no matter what they claim. Second, Aoun cannot afford to lose his bid on the presidency, not for six years and especially not to a powerful and popular figure like the army chief, who would certainly threaten Aoun's own popular power base.
Third, at the moment the negotiations are between the 14 March and the 8th of March coalition, which hold the necessary MPs to enable a two third quorum in the parliament. But once Suleiman is elected the initiative will move from their hands to the hands of the president and he will be the one working on a deal with the 14 of March controlled parliamentary majority.
In the end it is all just a power struggle. This was the case since the Syrian army withdrew from Lebanon and this is still the case. It is a power struggle between two coalition, one advocating democracy and liberalism; the other, well judging by its allies Syria and Iran, i will leave it to you to figure out what they are advocating...