Who would blow up the pipeline? The military? Is it guatanteed that the military would follow such an order? And who would give the order? A protester on the streets?
I see the biggest problem is nobody is really in charge in Ukraine.
But if you look at Iraq, Afghanistan, and the 21st century, it just seems crazy to do that. An army movies in? Well, your roads are going to be unsafe, because IEDs are easy. Your pipelines can be blown up by just about anyone. City streets will be completely unsafe. Snipers can make public gatherings a thing of the past, and suicide bombers can enter public buildings at any time.
Ukrainians might not be completely crazy (not so many Muslims there), but I'm not sure modern nation states still have the capability of taking and holding ground the way they used to. Armies may have less utility than one might think -- unless the local population wants the army to be there.
Certainly our army, which is the best in the world, and superbly equipped, has had a lot of trouble winning wars.