The Dominion has a unique system of government, most of the Dominion species have never seen a Founder, the majority of changelings have no actual participation in the day-to-day administrative matters which are left to the Vorta and Jem’Hadar. Odo succeeds in maintaining the internal stability of the Dominion and keeps its borders closed, this is explained in the novels.
In this sense, the changelings have to negotiate the exact borders of the Dominion in GQ and its future direction of expansion. As long as they realize that attacking solids from AQ and BQ will result in more complications, they will have to confine their activities to their present territories in the Gama Quadrant. Respectively, any exploration attempts in the GQ should not infringe their territory and AQ and BQ species should not colonize planets that belong to the Dominion or are in their sphere of influence. In this sense, a kind of buffer zone or DMZ seems to be a good idea.
By the way, Jankata Accords signed by the Federation and the Cardassian Union postulated that “no species shall enter another quadrant for the purpose of territorial expansion.” However, the Federation continued to visit the Gamma Quadrant so Ronald D. Moore stated:
"The Dominion does not own the entire Gamma Quadrant. We had explored the GQ for two years before encountering the Dominion, so it's not as though the wormhole opens up in their living room. There are other races in the GQ that are not part of the Dominion and the Ferengi at least have established trade with some of them. When the Dominion told us to stay out of the GQ, it was as if China told the US to stay out of the Yellow Sea. China is the big boy in this neck of the woods, and you better take their warning seriously, but at the same time we have trading partners and allies there and hey, freedom of the seas and all that." (AOL chat, 1997)