Is there any difference between the wifi chip and the 4G chip in terms of how it gets populated to the PCB?We definitely need ED's advice on that case. All I can reply is that the 4G module is seperated from the PCB, so that it's not making two versions of it. The WiFi chip is not.
Only ED will tell if he's willing to pay for the extra performance.
I'm not a hardware person, but as far as I understand, all of those components (wifi chip, 4G chip, eMMC, etc) get populated to the PCB in an automatic process where you basically give a machine lots of unpopulated PCBs and some reels with components on them, and then it automatically puts the components where they have to be, based on high-precision robot placement of every single part. At least that's how it looked in those Pandora ReBirth production videos.
There would essentially be one production run where the 4G component reel is present, and another run where it is not present, so there are then two different versions of the populated PCB.
What I'm proposing is to get one reel with 14 EUR wifi chips, and one reel with 28 EUR wifi chips, and use the 28 EUR reel in the production run where the 4G chip gets populated, and the 14 EUR reel in the production run where it doesn't.
Since those two wifi chips are basically identical in terms of pin layout etc, it should be as simple as that. Since there are two distinct production runs needed anyway, this does not really add any significant complexity.
I think both of these versions need to be available right away from the start. If there's sufficient demand, then ED can always make intermediate models in later batches: cheap wifi plus 4G, expensive wifi without 4G, different sizes of the eMMC etc. But for the first batch, I think it makes sense to make only the cheapest and the most expensive models. I suspect that early adopters generally either want the cheapest or the best, not some subtle mix.