I remember some typical RMA-style graphics about infantry of the future; unlike the current fashion of Robocop-like suits and exoskeletons those 1990's artist's impressions showed infantrymen as forward observers: Their weapon was merely for self defence (PDW; not full-blown assault rifles), while their main firepower was in their ability to call fires on target by radio.
The idea conveyed was that a team of two men could devastate a tank company, and this would be the infantryman of the future - not a specialised forward observer. The forward observer was the infantryman of the future.
I instinctively rejected this for years, but I also gave it a tiny chance: I was trying to figure out how and why this could possibly work out in some way or another.
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Back to the Second World War; as German infantry became rare in 1944 and the Eastern Front to be held still extended to more than 2,000 km the primary method for defending said line (more a discretionary string of positions) was to work with massed, quick artillery fires. The majority of attacks that were foiled were apparently foiled before the attack reached small arms range of defenders; by artillery fires on marshalling areas and approaching troops.
The weaker the infantry line, the more important was reconnaissance and artillery.
This approach had its limits, but also many successes. It's still an important one for 'economy of force' missions. These missions are necessary because the main effort requires a great deal of strength, and all other efforts must only be resourced enough to avert disaster (Schwerpunkt idea: Resource your main effort as much as possible to maximize the odds of success, and divert only as many resources to other tasks as required to avert disasters elsewhere).
My typical opinion on this is extremely close to Jagdkampf without some unrealistic expectations, and thus not noteworthy.
Let's see whether "forward observer" future infantry could succeed at least in this economy of force role:
Their survivability would depend on stealth by a great deal, and small team sizes surely enhance stealth. The alternative would be platoon-sized elements, but that would not be as economical, and possibly lead to more casualties even though probably less teams would fail entirely.
Economy of force missions may succeed by bluffing (deterrence), but once the hostiles decide to attack, the defence would be forced into a delaying action. It's unlikely that this delaying action could succeed enough to stop the attack entirely; it's a rare occasion historically.
Now it's obvious that 'forward observer infantry' calling in fires would cause some attrition to the attacker, but would they slow him down? Actually, lethality forces caution (or extreme rapidity) on an attacker, and this may very well slow him down a lot (example article). There is a point at which more caution and slowness is no better than dashing forward, though.
One of the principal problems of delaying actions with indirect fire is that the hostile ground forces would not need to bunch up ("mass") for duel situations; they could disperse. Dispersed forces are no efficient targets for most indirect fire support, though this changes with PGMs to some degree.
Forward observer future infantry
indirect fires support
Now let's add a third element to drive up the risks of offensive action for hostiles and bolster the morale of the forward observer future infantry: Quick reaction forces.
Typically one might think of heliborne forces because of their undisputed ability to traverse all kinds of terrain at the speed of a racing car on a racing track. Motorized companies could fit the bill just as well, though.
Their duel combat capability would force the opposing forces to bunch up again, and to be extra careful in many other ways as well.
Finally, there's a crossover between quick reaction forces and indirect fires support; close air support by fixed and rotary wing aviation. This one would only intervene if a major drive forward by hostile forces was actually observed already.
One could call said "forward observer future infantry" "skirmishers", "sniper teams" or "long range recce teams" as well. They could - combined with unmanned sensors - be an answer to economy of force missions if a highly elastic defence that readily gives up much terrain for military advantages was tolerable in the political arena and feasible with the ground forces' institutional mindset.
One might even extend it forward, as classic long range recce patrols, in order to gain depth. This is probably why I was able to look at the RMA-esque idea at all; I've been thinking about LRRP/LRS myself a lot since it became known that guided rocket artillery can provide effective fires to 80 km and beyond.
In the end, this whole text just made the case that maybe the delineation between infantry types should not be between "light" and "mechanised", but between "main effort"/"QRF" and "economy of force"/"skirmisher" type infantry, with the former being about employment in battalion battlegroups and the latter being about dispersed small unit actions.