Further, it is often argued that the F-18 (or Eurofighter) will become unsustainable around 2040 but (a) that's still over 20 years into the future and (b) that's approximately when FCAS EIS is planned.
I expect the Eurofighter to last longer than that because it has multiple operators. The SH only has two currently and shortly a third but the RAAF has a clear stated intent to remove from service and Kuwait is as close to useless as they get.
AFAIK the EA-18 carries a total of 5 pods: 1 centerline for low-frequency, 2 on the wing for medium frequency and 2 on the wing for high frequency. That centerline Terma pod can probably only host one of them (though the high-frequency pods are smaller, so maybe there's some extra room for them). You'll also need air intakes and exhausts to power and cool the jammers.
The EA-18 is a stand-off jammer so it requires a heavier investment in jamming pods but even then, it is unlikely to actually operate with 5 pods given the significant drag that creates as well as the fuel it displaces. A quick google image search shows the standard config is three pods and two tanks.
Obviously the dedicated EW variant of a multi mission pod is going to have cooling and power. Noting as well that the F-35 having two bomb bays could, with sufficient heat management, also hold additional jamming equipment in those locations and merely deploy the antennas around the airframe. It does that all while still carrying the full internal fuel load in a less draggy airframe which would provide a range significantly greater than the EA-18G.
But the above is irrelevant in the German case.
And my point still stands that jamming involves sending a powerful rf signal towards the enemy, which entirely counters the point of stealth. The only advantage I see is that it becomes easier to get out of precarious situations, e. g. when the enemy launches radar guided anti-jammer missiles.
Think about the context. As a stand-off jammer the EA-18G isn’t typically deployed far enough forward to be within the range of those types of systems or if so those systems are focused on the threats the EA-18 is protecting. The aircraft also typically operate in pairs and have the ability to cooperate, including switching on and off their jamming equipment as required. They also typically operate in concert with other platforms to do some of the electronic sniffing for them, such as RC-135s. Few nations also have the SAM or A2A missile depth to waste a shot for a home on jam scenario, when with jamming switched off that missile shot becomes useless.
Using a stealth platform allows the aircraft to potentially be deployed much closer to the area of interest, increasing jamming power and better supporting the assets. When it switches off the jamming it has the ability to return to a much reduced detection configuration. Detecting the jamming is also dependant on the jamming technique used.
I don’t think either of us knows how effective that jammer will work in a near peer threat situation but the US experience with Red Flag should give an indication of how it operates. We certainly don’t hear too much talk of Blue Air Jammers being targeted and destroyed in these exercises.
However, stealthy assets that are protected by a jammer can probably become even stealthier. So a combo of F-35 + EA-18 makes perfect sense. In the context of European forces, many other nations have ordered the F-35 but none have a comparable EW platform.
The in-built jamming the F-35 has, the ALQ
-239, should more than allow for it to penetrate defences to the degree necessary. Any EA-18G operated by a European Nation would be protecting legacy aircraft, not 5th gen assets in a future conflict.