There is cross-tolerance between benzo's and zolpidem, but it's not like a benzo to benzo tolerance. It's a light cross tolerance. Benzo's are cross tolerant with barbiturates, but again it's a very light cross tolerance.
phatass, zolpidem comes in 5 and 10 mg tablets. Zopiclone comes in 7.5 mg tablets.
Also, not all benzos suppress deep sleep or disrupt REM sleep. Temazepam is a benzo that has NO effect on REM sleep. Lormetazepam, which is a 3-hydroxy benzo similar to both temazepam and lorazepam (which are also both 3-hydroxy benzos). Lormetazepam (chloro-temazepam or methyl-lorazepam) at 1 mg does not alter REM sleep either, but 2 mg it does but nothing significant.