More zones = longer spawn.

Describe your suggestion in short

Different respawn time based on the number of zones your team has. The less zones you have the quicker the spawn. Let's say the base respawn time is 20 sec. Having each zone would increase the spawn time by let's say 10 sec. So if your team has 1 zone you have 20+10=30 sec, and the other team has 20+40=60 sec

Why do you want this suggestion?

That would make it easier to defend the less zones you have and will make it less likely to have zones undefended, so would somewhat decrease the advantage of rushing

Extra details

This makes sense from RL perspective as well - the closer you are to your base the less time it takes for the reinforcements to get to the frontline and vise versa As for the inevitable criticism of it being a hidden mechanic, I'd say it can be written on the spawn button (or close to it) and anyway it doesn't have to be explicit for the player, to do it's job