I don't have a pool yet, but we will be having approx 1500SqFt of mortared (wet lay) thin paver overlay around our future pool this fall. We live in Ontario Canada, so our climate is comparable. We've installed 2 flagstone patios on our property in the same manner, and have had no issues since they were installed 4 yrs ago (and this past winter was a killer!). Our property is one big sheet of limestone though, so there isn't much wiggle room to cause heaving. For the other patios they brought the grade down to the limestone base, then compacted the aggregate base, poured the cement, put the flagstone in place & mortared it. (I may have missed a step or so, but hopfully you get the point...forgot to mention o-hoses were strategically placed for drainage, and the cement based installed with the slightest slant to aid in run-off). We are opting for the wet lay vs the dry lay for our future pool b/c we find it looks much more finished. We have many other friends in this area who have either pavers, dry lay thin pavers over a cement base or wet lay over a cement base and no complaints yet.
Does your present concrete base have a really good compacted base layer? I think that a good base layer and proper drainage is the key.
Good luck!