Base defence, how to not get pinned inside your own doors.

[IMMentat]

OK this one has long been one of those things we just accepted about PS1.
After a certain point in a fight, your base walls were the other teams walls, your turrets were just so much scrap, and your doors were areas of instadeath due to MBT camping nearby and the enemy spawn point being closer to the door than your own.

I'm hoping this will not be the typical scenario in PS2, but just in case, here are a few ideas for countering these.

1.
Gunports/firing slots within the pillars of the base walls. (think of arrow slits in a castle)
I dont remember the outposts just outside a base ever being used due to them being low, inaccessible and easily attacked/taken, shifting these to within the base walls themselves or by providing an entryway within the base courtyard would go a long way towards helping the defenders counter-attack/defend against swarms of enemies, these would be 2-way windows so attackers can also returh the favour.

2.
Tunnels into the base walls accessible only from witin the base so that turret repairs/re-arms and manning are not done from a completely exposed position (as a result, repairable objects would limit number of active repairers to 3-5 and item death (of an object that goes/started above 25% HP) would result in an explosion that damages anyone nearby, maybe 50% health loss.)

3.
Bases that do not allow vehicles into the courtyard, less support means easier to defend against sustained attack, and makes for some variation in the fights. (added mosty because of the PS2 video I saw, had not considered this otherwise)

4.
More variation in base layout.
In PS1 every base had a similar basic layout, i know the PS2 bases are a lot bigger and a lot different visually, but unless this also reflects in the general layout then fights will eventually happen the same way in every base. (specific tactics for each base would eventually emerge but this is more acceptable)

5.
Provide more options for spawn-points to allow the defenders an alternate place to attack from.
If Lord of the Rings taught me one thing its that a large sieging force will inevitably grind down even the best made defences.
One of the best ways of countering a siege is either by providing alternate routes out of the base from which to attack (sally-ports, prefferably above ground level to make them 1-way trips), or by having the cavalry ride in from the sunrise and catch the attackers in their exposed bits.

PS1 locked spawning down to a saved base, a saved AMS, the nearest base, the nearest tower and the sanctuary.
This sounds like a lot, however by late into an attack the AMS would probably be dead/hacked, the saved base would probably be the one your in and the tower fallen even before that. This leaves only the sanctuary (equivelant to giving up) and the same place you died to defend left to spawn at.
Not enough I say, defenders need the option to load up and counter-attack from a less swamped position. Spawn options of the 2 nearest bases should be enough for this.

What you think, and are there any other ideas?