Tanks, Vehicles and Mech in 5th edition: Changes for 6th?

So in the latest review of the latest Forge World Land Raider variant we noticed how poorly balanced the Achilles was. The weapons themselves were pretty good but lack of transport capacity, assault vehicle status and the combination of ferromantic invulnerability was counter-intuitive (basically the Achilles is quite happy to run into the teeth of an army due to it's melta immunity yet it doesn't have the capacity to deliver such units as Terminators). However, ferromantic invulnerability is where the balance issues come in. Armies which rely on melta and lance weapons for heavy anti-tank become very Ork-like against the Achilles; i.e. bad against AV14. Armies like Tau and Imperial Guard who have weapons which ignore this special rule (i.e. railguns, S10 Ord, etc.) however don't care (it's just like a normal Land Raider to them) and any army built around multiple Achilles enters a rock-paper-scissors 40k. This sucks. However, it does raise a very important part about vehicles in 5th edition and the glaring need for an improvement.

What? Did Kirby just say mech needed to be improved? Yes indeedy. We all know vehicles right now are excellent choices due to their inherent survivability. This isn't to say mech is the only way to play 5th edition but vehicles and especially transports are a highly viable option compared to 4th edition. With the changes to the vehicle damage chart and the importance of AP1, guns like meltaguns have become very important (not to mention the cheaper cost) in a lot of armies. Whilst some immunity to melta is good (i.e. Stormraven or Avatar), when a unit which is generally only killable to certain armies through meltaguns, making it immune to them is poor balance. However, for guns like these there is very little difference between AV10 and AV14. Sure there's ~10% difference between the two in terms of meltagun effectiveness but AV14 is often far more expensive than AV10 and no where near as spammable.

What this has lead to is more mech armies with lots of light to medium (i.e. inexpensive) tanks compared to a few heavy tanks. This comes down to a 35 pt Rhino being pretty much the same in terms of survivability as a Land Raider against some of the best and most common anti-tank out there (i.e. meltaguns). This sucks for anyone wanting to use an expensive, heavy tank. Considering the divergence between point cost of low AV and high AV tanks and the similar ease to which certain guns can drop both, there's an inherent imbalance between cheap and expensive tanks. Cheap tanks are generally better as you can get that many more of them. What this means is in some way we need to differentiate from light and heavy tanks in some form not just based on Armor Value.

So, here's where we come in with potential changes and discussion. Just so we're clear... I think 5th edition is great and rather than an overhaul it just needs tweaks (like 5.1 or something). Tanks in general don't need to be touched really, maybe making the explosion more deadly to guys inside (up the strength?) but I feel the vehicle damage chart is fine as is. However, there are a couple of ways we can fix the lack of survivability divergence between cheap and expensive tanks whilst still keeping them balanced within the system.

One easy one is adding structure points based upon expense or armor value (or arbitrarily). For those not familiar with structure points, tanks start with X structure points and when a wrecked/destroyed result is inflicted upon a tank, subtract 1 from X. When X reaches 0 the vehicle is destroyed. So a normal and cheap tank like a Rhino would have 1 structure point whilst a more expensive tank like a Land Raider might have 3 structure points. The problem with this is anyone without the capability of dealing with heavy armor normally (like Orks atm) are now at an even worse disadvantage against high AV tanks. However, it makes the heavier tanks more viable as they are less likely to be one-shotted and basically be an expensive heap of junk. This is probably the simplest and easier implementation but getting the structure points right is important to maintain balance. I.e. most tanks stay as one but heavier tanks like Russes or Hammerheads might have two and only extremely durable tanks like Monoliths or Land Raiders would have three.

Another way is to use different vehicle damage charts for different tanks. Problem with this (beyond being more complex when GW seems to be moving towards streamlining), to make the difference between tanks extreme enough might make lighter tanks very easy to pop (i.e. 4th edition easy) and still leaves heavy and expensive tanks vulnerable to being one-shotted. Not a fan of this concept as it doesn't really solve the problem and just takes light mech back to the darkdays of 40k.

A further option would be to have burnable or mutable armor. Currently upgrades like spirit stones, extra armor, etc. are pretty useless with their current expense on cheaper tanks but quite usable on more expensive tanks you want to keep moving. Changing their rules so they can be 'burned' to downgrade or nullify an effect (like a structure point there) can make tanks more survivable but due to their increased cost, not seem worth it on the cheaper tanks which you spam. For example, change the ruling of EA to negating AP1 effects/providing a -1 on the damage table which can be "burned" (used up) for a one-off -3 (you no longer then get the -1 effect). This can stop heavy tanks from being one-shotted early and is obviously a good investment whilst putting them on all of your cheaper tanks is going to add up quickly. I like this concept though it would need to be refined a bit more as it doesn't make heavy tanks really hard to kill for some armies (i.e. like structure points) and burnable items aren't exactly new (combis, smoke launchers, etc.).

So these are just a few ideas batted around before in the chatbawks and on YTTH and I thought with the recent release of the Achilles rules it would be a good time to discuss it again. Any other ideas or thoughts on the above ideas or general thoughts on vehicles in 5th edition currently?