The Kent folder has a couple of problems.

One is the frame design, with the BB attached behind the seat tube; this makes for rather bad ergodynamics. I can't imagine why they did this. It can't be fixed.

Another is that it's hard to get both the seat high enough and the handlebar low enough; the designer of this bike, like many folding bikes, thinks people are short and want insanely high handlebars. The taller rider will be bothered by the low seat; the shorter rider will be bothered by the high handlebar. Somewhere between the two there may be a rider for whom the bike can be fixed but, depending whether you have the right parts in the bin, it may be expensive.

Finally there's the gearing. The six-speed derailleur is the worst; all six of them are too low. The Nexus-3 is great improvement. I have a six-speed that I have modified to a three speed (sturmey archer) and can attest that improving the gearing in this way more or less fixes the problem.

Bottom line, I think, is the Nexus 3 speed hub fixes the worst of the bike's problems but, obviously, doesn't address the others.

I should add, I really like the Kent's unusually short (152 mm) crank arms; most bikes come with 170 mm arms, which I find too long.