I REALLY would love to see someone run a test airline with the CRJ 100/200 only. Do what I did trying to succeed with a fleet of Fairchild a/c. Make a diary/blog about it.
I am doing that right now in Sofia, although I've had to expand my options a little to their larger family members. I managed to earn enough from my initial CRJ100/200s to afford leases on a nearly CRJ700 and a new CRJ900, which is nearing delivery. Luckily when I started leases on the used market were near standard, as now every CRJ that appears has a much higher leasing price and would be unfeasibile.
It's hard work and every fuel rise dents profits massively, but profits are around 100-200k most weeks, which pay for the C-checks fine and eventually allow for the new leases.
The majority of the routes available aren't partcularly close, but there are a couple of domestic routes that have ~200 demand.
Progress is just very slow, but I'll be sticking with CRJs for the duration of the world to see how they fair.