I sat through the G.I. Joe sequel, a couple of days ago, and saw something that made me wonder two things: one, why don't any IG tanks have missiles, and two, could you mount something on them?

Now first, please allow me to extrapolate. I am familiar with Manticores and Deathstrikes, so I know that the tanks can carry rockets, but I am thinking more like a pintle-mounted rocket launcher; something on the scale of the people driving the tank's weaponry, but affixed to the tank. On top of a tank the Rock drives, there is a small, six-barrel rocket launcher, fired by controls inside. I don't see why a similar rig couldn't be affixed to a Chimera, or maybe even a Leman Russ (makes me wish the IG got a Predator-style tank, but the best must be saved for the Space Marines). The rockets could either be remote-fired from inside, require someone to poke their head out, like some other weapons, or even be operated by Machine Spirit. It could carry 4-6 missiles (frag or krak, whatever the situation called for), and add an extra layer of armament to the team. Other than a possible angered Tech-Priest, raving that you have altered a pattern that has worked, and been in use for millennia, possibly the same TP who you will need to mount this optional weapon system, is there anything stopping a Mechanized force from adding such a weapon to a tank? Would a TP belly ache, or just think it's a fine idea?

The Havoc Launcher mounted on Chaos vehicles (DW Rites of Battle ) is precisely such a system, so any loyalist TP would be very down on adding it to an Imperial vehicle, though a TP might be persuaded to mount multiple Hunter-Killer Missile Launchers to a Leman Russ-sized battle tank.

APC’s with an anti-tank capability through anti-tank missiles are nothing new in modern armies and the Germans pioneered close-in anti-personnel vehicle defense with frag grenades in WW2.

So it exists. But would it exist in WH40k and then in the Imperial Guard?

First off, angering TP’s is a death sentence. They take desecration of the machine spirits pretty serious. And it’s unlikely that anyone outside the higher levels of TP-hood would have the knowledge to make such an additional weapon system work unless it was restricted to adding another heavy stubber to the vehicle. So a bunch of Armoured Fists adding additional weapons without permission is very unlikely. And it’s not just sheer intransigence at work. Adding weapons to a vehicle means more weight which means all systems are under more pressure thus leading to increased wear & tear. And heavier vehicles need more fuel. Extra weapons need more ammo. Thus the entire logistical system is put under increased strain. Any weapon system is thus paired down to its most basic yet still effective minimum to ease logistical requirements. In Only War, which focuses on grunts, these are important considerations.

The fluff suggest it can go either way. In theory, the TP’s are technologically rigid and conservative and any field modification unsanctioned by the proper authorities will be punished (usually by several additions to the TP servitor pool). And sanction only comes after centuries of debate at the highest levels of TP-hood. So that would indicate a firm NO!

Yet the Imperial Armour books suggest field modifications are not unknown. Under desperate circumstances, TP’s do allow field modifications, usually aimed at coping with local conditions or to alleviate critical deficiencies in supplies/weapons etc. Usually, these modifications remain localised but sometimes they are picked up and sanctioned for general use. Preferably if the modifcation can be linked to some kind of prior version of the same vehicle, now lost to antiquity…but rediscovered by divine inspiration in a time of need.

All of which means any GM can decide how he wants to play this. I’d suggest it would be difficult (lot’s of red tape and a constant hassle getting extra ammo) but possible. My GM philosophy is to never say no but make my players really sorry they asked….

There is a Chimera variant, the Chimerox what has a twin-linked missile launcher instead of the normal multilaser (and a reduce transport capacity).

Also, TPs are onyl concerned with the "official" designs like the Chimera, Leman Russ, Rhino and such. If you "liberate" some TZK-788002 White Tiger light tank from the arsenal of the local renegades/PDF/whatever then you can do whatever you want with it because it is not an "official" design.

There is really no reason tanks with a configuration like this can't be 'standard' pattern.

The patterns given in the books are mostly limited to what GW has already put out, which in turn is limited by what GW has been willing to create miniatures for. But I think none of the designers involved has ever claimed the list of standard configurations published is exhaustive of the number of standard configurations that exist within the setting.

Just think of a cool name for the configuration, maybe the names of some forge worlds famous for creating tanks of that configuration in especially high quality and numbers:

In the tabletop Codex: Imperial Guard, they are called Hunter-Killer Missiles and are an upgrade available to any IG ground vehicle. They are single shot krak missiles with extended range (in the tabletop game they have "unlimited range" which means they can target anything on the battlefield).