If you’re fighting another green army, you probably don’t need ECM, after that you need it, which is why we need to work on making it lighter.
Just not true. God this myth needs to die. Yes, put it on vehicles, because a) they can carry it, and b) vehicles are forced through chokepoints a lot more than foot patrols are. The threat is higher and the cost is lower. But vehicles and VIED are a very different beast to foot IEDs and ECM.
In all cases except for somewhere like Sangin, varying routes, avoiding vulnerable points (hereafter: tactical patrolling) is an effective counter to foot IEDs. The basic observation is that it is functionally impossible to RC-IED an entire area, so it doesn't happen. Resourcing, digging the things in covertly, and identifying routes prohibits doing it on a large scale. 'IED belts' were (again, Sangin aside) largely a myth, because it was impossible to lay them. This is just tactical patrolling: skills that we knew in NI, I was taught at Sandhurst, and we almost universally binned off in Afghanistan. The ECM 'need' resulted from FIXing ourselves with static locations, then compounded by a lack of tactical patrolling. Most of all, ECM only counters a relatively small proportion of IEDs, which weren't even the favoured / most advanced type (that would be PPIED), so any enemy which discovers their RC-IEDs don't work will almost instantly switch type.
The IED war was a tactical failure on our part, not a tactical victory by the other side. Foot ECM was a highly detrimental (because weight, and it limited freedom of action to the bubble: it unnecessarily scared soldiers and prevented tactical movement and response) and minimally helpful (because almost as soon as it appeared, RC-IED disappeared) element of that failure. We have decided to ignore this lesson for reasons that are unclear to me, but I would be unsurprised if they didn't link to our regular boast that British industry produced the best ECM in the world.
Before people get on their high horses, I tested this in contact personally over many patrols, as well as shared notes with units like PF who did the same: we all came to the same conclusion that tactical patrolling drills reduced IED strikes to almost zero, and this included areas which had been identified as "IED belts". We did this without carrying ECM, because we wouldn't have been able to cover the ground the job required if we had. Moreover, in several operations since (in a sub-green army opponent) foot ECM has been binned, so clearly it is possible.