The millions of displaced Syria n's in the countries surrounding Syria need to be materially well supported in their camps as do the countries them selves . Europe and America can well afford to do this.European borders need to be enforced and these people to be assessed.Some will stay and some should be returned under agreement to some of those neighbouring countries.Returning them to fight for their countries may be a misnomer, Somalia is parcelled up as usual between warlords/factions, I presume.
Iraq is in bits including a large bit held by Isil.
Syria is a shifting tapestry of bits of ground held by various groupings.A young Syrian who is anti- Assad and whose other option is to fight for Isis may choose to fight for neither.
Also remember the civil war in Lebanon (similar ethnic divisions to Syria) ran from 1975 to 90/92.Hence no easy solution likely.
Western military involvement , apart from air strikes, which may or may not achieve much, will not involve "boots on the ground unless a few trainers.Russia has some military trainers supporting Assad who they back.