Egypt had been discussed a few years ago, as a possible peace-keeping force in a Post Civil War Syria.
Their Military is Arabic-speaking, and large enough to be feasible (if International donors pay the costs).
Egypt has a history, within the lifetimes of people in both countries, of participation in the “Pan-Arab” or “Arab Nationalism” (under Nasser) philosophy that the Syrian Ba’ath Party is still officially tied to. So they might be the most acceptable option to the Assad Regime.
This marks an interesting shift from the clearer Sunni/Shia divide of past decades, when Egypt and to a lesser degree the more secular Turkey, were viewed as the main Army of the Sunnis.
Now there seems to be a increasing confrontation within the Sunni side, between a now much less secular neo-Ottoman Turkey (and Qatar), supporting islamist revolutionary movements in the region (like ISIS and the Muslim Brotherhood), and an Egyptian/Saudi alliance, defending the old regimes.
Hostilities are escalating between Egypt and Turkey in Libya. Egypt engaging in Syria would be a pretty major escalation of the conflict between those two large Sunni armies.
Egyptian peace keepers might allow for a face-saving Iranian withdrawal from Syria, without a Turkish takeover - but it would be a pretty huge stretch for Egypt. Some major bill payers would need to be committed to make it succeed.
The blast in Lebanon is changing the balance inside Lebanon. Will it be enough? Depends upon what is uncovered examining the blast and who had control of the explosives.
Not sure I believe the Ammonium Nitrate explanation. There was talk about rocket fuel. Judging the photos of the blast, might support that view. And it appears the majority of the blast was vertical. Yes, in spite of the blocking of the blast by the silos, which helped, the damage was huge. But it could have been much much worse had the full force been at ground level. It is unclear what triggered the 2nd blast. I've read some plausible scenario, but no clear explanations.