I know this has been discussed once in the past. But I feel a need to bring it up again. Yes, I'm new. Hi.
I'm planning to buy a Brompton in the near future but I really want the versatility of having a greater selection of gears.
Here's what I'm proposing.

Can I replace the 3 speed hub with an 8 speed hub? I'm looking at buying a used L3 and it's got a 3 speed SRAM hub.

I guess the big question is about spacing. Can it be done? If not, what alternatives are there?

Schlumf looks like a last resort.
Rohloff is stupid expensive.

I read somewhere that Merc has an 8 speed version. I may be interested in that, but I can't find one anywhere online.

I want a folder with the compactness of a Brompton and the versatility of an 8 speed hub.

Help!