Striking Assad can be very helpful if it is part of a plan to support and empower the SDF. Other than that, it will probably do more harm than good.
Before you strike Assad, you need to know who would benefit most from such strikes.
It seems that the officials who wrote that memo still believe in the old story about a moderate Sunni Arab opposition in Syria that needs to be supported.
Many Sunni Arabs in Syria are moderate, but the most important Sunni Arab militias in Syria are not moderate. Those militias are founded on jihadist ideologies.
Trying to organize moderate Sunni Arab rebels into an army that would defeat the jihadists is an unrealistic idea. I think it has been tried already and proven to be a failure.
The Sunni Arab opposition has very serious cultural problems. Many people in this opposition do not really believe in a pluralistic democracy. If you ask them, they will tell you that they support democracy, but they will also tell you that Syria in the 1940’s-1950’s was democratic and did not have any problems. They will tell you that hateful tyrants such as Al-Quwwatli and Al-Shishakli were democratic rulers. Everything was perfect until non-Sunni demons took over the government. The word “democracy” for them has another meaning than liberal democracy. It really means Damascene fascism.
The SNC have no problem with the Damascene fascism of the Assad regime. They want to continue that fascism, and if they have the power, they will try to force it again on Syria. Their only problem with Assad is that he is an Alawi. If he were Sunni, they would not have rebelled against him.
It would be very foolish of anybody to empower that opposition. This is the mistake the British did when they invaded Syria in 1941. The British helped Quwwatli set up the Damascene empire in 1943, and the result was an autocratic regime that collapsed only five years later in 1948, and then chaos ensued and never ended.
The SDF have a realistic view for Syria’s future. They do not want to set up a new empire. They say that they want a decentralized democratic government. What they want is similar to the Iraqi government that was set up by the Americans. That government is commonly viewed as a failure, but the principles on which that government was founded are not bad. The problem in Iraq is not the political system but it is mostly the bad politicians. For example, Barzani keeps pushing for Kurdish secession and keeps fueling Arab-Kurdish tensions because he is a racist ultranationalist tyrant. By the way, he is now an illegal president of Iraqi Kurdistan since his term in office ended long ago.