I have a Brompton 6-speed. The gear ratios are really awkward in this model, with huge differences between the 3 IGH gears, which require one to constantly compensate the gaps with the 2 speed 'cassette'.

3 gears is something I can live with, but the gaps in the BWR (Brompton Wide Range) are just to big.

The question: can I swap the internals only, with internals of a 'normal' Sturmey-Archer 3 speed?

Like this: HSX144 SRF3 / BSR/ A|-Brommieplus-Products

Is it an easy task for someone with plausible experience in bike mechanics?