this is idiotic, why not allow your enemy to spawn at your spawn as well? there is no way to force someone to spawn somewhere else, until then this is just a stupid idea.
To make capturing spawns an option?
If someone manages to kill the people around a catapult, they can take it over. Same if they take an area with a healing tent.
If you manage to push your enemy away from a place where they have major siege equipment made, without destroying said equipment; then why should they not be rewarded with it?
With my additional idea we also make forward bases capturable. If everyone keeps spawning on the same one, there will be no possible way to capture it. Unless you managed to convince your enemy to de-select their forward base, then they will just respawn on it until it is destroyed. If you manage to push an enemy out of an area while they have a forward base, you get a free forward base.
Nobody forces you to set your spawn at a forward base. Comparing spawning at a forward base with spawning at your team spawn is silly.