Yes gussets were 2012 by the look of it, Had a quick search... I might still be cheaper buying a full bike, tyres and wheels seem to be around 600 squids on their own. Anyone show me otherwise?
Why is passing CEN or other safety/quality tests seen as a bad thing ? Without such things cars would still be the death traps they were for most of the 2Oth century.
Anyhoo gusset or not TK would have to be going some to bust a fatbike frame and we should be twisting his arm to buy it
If the frame is 135mm offset then build your own using a standard hub and spokes laced to a rim from say http://www.Robsson.de who have oodles of choice at very good prices. If 170mm then Salsa do an adaptor to take up some dropout space to allow fitting a 135mm hub. BB's from the world of DH can be used for widths up to 100mm and are available new and used. Tyres can be had for £50 each and innertubes for £6 a throw.
Everything can be done on the cheap plus second hand kit shows up every once in a while.
All fatbikes are going to be sedate compared to your existing rigs, I doubt you'd notice unless you'd ridden many other fatbikes to compare with. The MukLuk is however aluminium and thus could be built lighter than a Pugsley.
£20 singlespeed nutted hub from CRC for front wheel, 170mm rear hub (don't know how much that would be), and get them built up by your friendly wheelbuilder?