This is true in today's great tools you can carry in a van or truck. Large enough bolt / chain cutters slice like butter.This is the MO for bike thieves. Have a van with a mattress in the back. Two guys to pick up the bike. Fast and somewhat stealthy as the van keeps the bike hidden.
A chain may slow down a thief but won't prevent them from getting it. If they want the bike, they're going to get it.
Then if that is not enough of quick, you can power plasma cutters in most truck and vans today. So just cut the thing in seconds with a plasma cutter.