I know that the first half of this is going to be a particularly unpopular idea.
Hearth fires need to be able to be passed through, even if they remain indestructible. There is an oft used exploit of building hearth-fires around a battering ram to create an indestructible wall, making them impossible to reach. This is an exploit of exploits. It means it's theoretically possible to create a wall that will stop even the most seasoned brick-buster, if one is simply willing to create enough alts to manage it.
On a similar note, if it were possible to pass through milestones, it would make building the automated roads much simpler, either that, or increasing the 'turn radius' of the milestone itself, so that it wouldn't be necessary to get so near before changing direction.
Either way, the hearth-fire exploit desperately needs removing.
(Admittedly, one *COULD* build a claim over said hearth-fires and remove them from being an obstacle, but better by far to remove the exploit entire by making them able to be passed through)