They're not "theoretical", they already exist. At least in MA, we only have two coal plants left and they're both looking at shutting down.
The natural gas infrastructure is a bit lacking. There was a shortage this winter when everyone was warming their houses (not cooking burgers), so a lot of places needed to switch to oil which we really don't have infrastructure for. Some higher capacity pipelines would be a good addition to more renewables such as off-shore wind power without needing to rely on coal.
Sorry, I meant 'theoretical' as in brand new stations or new capacity at existing stations, which you would need to address if you are looking to shut down existing coal sites. Of course, if your currently built capacity is already sufficient to forego the generation from the coal plants, then there's no barriers...other than, as you say, cold cold winter nights where the gas supply can't keep up with the domestic load, much less industrial.
Don't get me wrong, I'm all for switching to natural gas generation in favor of coal generation, but people should realize that there is a whole lot of infrastructure required to make that happen. It's not 'just' bigger, stronger pipes (although that's certainly a huge component...and not a simple process to install), it's also upstream compression, alternate supply routing (probably with additional compression), cathodic protection to keep the pipes from corroding, and in some areas it's additional specialized instrumentation required such as moisture, heating value and H2S analysis.
In comparison, coal can be trucked to site, burned and produce steam generation with minimal fuss. It's not hard to see how coal got it's stranglehold...