Most bases covered in obsidian have obviously had a lot of time put into them. After doing such a tedious task, people make sure their base in unraidable. If you have a lot of time on your hands, this is easy to do. Eventually, almost everyone will have bases like this. It will be impossible to raid, which would take all the fun out of factions. If you're not going to add Obsidian breaker, you should at least add creeper eggs into the shop. This would allow you to blow up chests while inside of a base. It may be possible to get inside of a base, but not break the chests using a cannon. Having creeper eggs in the shop would allow players to place the eggs in claimed territory and get the items that way.