IIRC when DL did the big LGA expansion, there were at least some flights to some upstate NY destinations like BUF that did use RJs with FC. I'm surprised that they're 100% CRJ-200s now.

If the OP is willing to spend a small amount of money doing a MR, given rollover, it would be better to try, within reason, to maximize the MQMs that one earns for the money spent or even to spend a little bit more to get a bunch more MQMs for rollover.

Alternatively, instead of looking for a really cheap way to get the 405 MQMs (actually 1000 assuming a DL RT), think about a nice little fun weekend trip. SEA is likely to be relatively cheap given the DL versus AS competition there.