Is it possible to place an SMD crystal on opposite side and connect it through vias?
You can do that, as long the frequency is not too high. A few 10's of MHz should be fine. As always, if the frequency is high, you should consider the signal integrity. The vias introduce impedance discontinuities, which can make the clock non-monotonic from the reflections. This is a problem, if you do not have a Schmidt trigger inputs. 

Another thing to consider is that it is usually more cost effective to have the boards pass through a one side pick and place process. It depends on your volume and manufacturing strategy. I've seen board where it is cheaper to go for blind and buried vias, than to put components on both sides.