[Suggestion] 5-15 minutes respawn delay after death?

No. You need different units to win and the evidence is right in front of your eyes; the only "combined arms" tactics in PS2 is the Zerging: move quickly a lot of foot soldiers by air and ground and have them supported by armor and ground attack aircraft moving all together.

Take the transport vehicles out of the picture and you will have only a mass of slow moving foot soldiers easy to mow down in the open. Take the foot soldiers out of the picture and you will have a mass of vehicles unable to support each other in urban areas and unable to conquer anything.

That's the great irony: everyone is talking about nerf/buff/instagib while the one and only incredibly crude tactic ever developed (the Zerging mentioned above, which is basically "create a snowball") beats down everything else.

Not what I said. I said "infantry", as in "a group of" rather than "any solo infantryman". But naturally you assume the worst-case scenario.

Where are these assumptions coming from? I only said "infantry should be capable of going up against tanks with the right loadout" and you instantly build an entire story around it based on random assumptions that are build in a way that it's unbalanced.

Yes, so why didn't you try to build a scenario that actually did work with that in mind? I've corrected people a million times on these forums about this exact assumption, so why are you still going on about it?

But you do make a good point: They all have a part in the puzzle. Unfortunately your idea of "combined arms" is "everyone does one job and is inept at anything else". That's not combined arms in any way, shape or form.

Nope, they shouldn't do just that. It should be far more. Having infantry on your side supporting you should be better than replacing those infantry with tanks, but that's absent from your idea's.

I'm not trying to reinvent the wheel, I'm trying to get you to learn what Combined arms actually is.

Segregation of arms is the opposite of combined arms! In real life combined arms means that infantry support tanks. They put down minefields for area denial, they spot targets for tanks or aircraft to bombard and with proper instruments they can even take down heavy armor without combined arms. Aircraft profit from having ground forces, as ground forces can spot targets, threats, attack enemy positions, deactivate enemy G2A weapons by destroying them or forcing them to redeploy to another area, deploy radar and even counter-measures etc.

Your idea of combined arms is completely ridiculous. Tanks don't just function till the infantry is at the urban area, where the infantry then goes from door-to-door and Infantry aren't useless in large open spaces where tanks roam. You aren't just re-inventing the wheel, you are inventing a square wheel without axles.

Despite the fast spawn times it does matter, and it matters a lot. What you fail to understand that in PS2 even a minute of no G2A weapons because they were destroyed is a win for your team. Just because the G2A weapons are back up within 15 minutes doesn't mean your act was useless.
PS2 is less about destroying enemy targets and more about controlling small area's. Sure they could enhance it, but that doesn't mean the current iteration is instantly completely flawed, and the spawn times are definitely not the problem. The ability to pull out anything in quick succession is one of PS2's strongest points. It means that you are never truly restricted in what you want to play, and that players can't suddenly be completely helpless and get farmed ad nauseum just because something else was destroyed. Adding weaknesses is a great idea, but it should be achieved elsewhere. Such as by letting players build their own logistical support system for ammo, revives, scanning enemies, protecting against hacks etc and letting the enemies destroy these.

Are you really trying to pass Zergs off as combined arms? Really?
Combined arms doesn't mean that you need different units to win. It means that having multiple different units you are stronger than having only the same unit. A good game will allow you to use a single unit, such as 100% infantry, to do anything you want. However using mixed battlegroups is better.

Zergs do not act with combined arms. Zergs are just as much viable if you use all infantry or with some bases only vehicles and one or two guys to cap. The fact that overpowering your enemy with numbers rather than tactics is superior is a flaw in PS2's system. The fact that Zergs sometimes have a semblance of combined-arms, as far as that's possible in PS2's stunted teamwork/synergy system, doesn't mean they are combined arms.

Vehicles can support each other in urban area's. That's kind of the point. Especially if you plant some AI weapons on top of one or two tanks.
And if you remove the spawnsystems (Sunderers) then yes, you get a whole mess of infantry. The thing is that a Sunderer fits perfectly in the Mechanised Infantry divisions. Especially if we ignore all the buffs to it's armor and armanents it's gotten over the years making it more a tank than an APC it still functions more as Mechanized Infantry transport than anything else.
Unless you want to make a case that driving a car is also combined arms and that those people are then tanks rather than infantry?

That's not Irony, that's just people trying to improve the overall gameplay they experience. Additionally there have been numerous idea's to decrease the viability of the Zerg while improving teamwork and combined arms, actual teamwork and combined arms.