ermm well there is Static AKA . . . who shoot purely AKA markers, Excaliburs, Vikings and Merlins.
As for why there isn't any sponsored AKA teams in the UK. . . AKA are still expanding purely on the demand of the products, this demand has mainly come from word of mouth not mass advertising. There also is no mass distributor for the Viking in the UK, so what do you expect??
AKA also are converting to producing markers rather than concentrating on custom products for other markers.
All I know is that personally I wouldn't swap my Viking for any other marker. .. well maybe an Excalibur
As for people wanting to customise there own Viking, products are slowly appearing, i.e. WAS Equaliser board (with eye), a No Rise for the Halo and other feed necks, Custom triggers and frames and AKA have just released upgraded Solenoids
Theres nothing really performance wise you can improve, built in LPR, low operating pressure although very efficient and extremely reliable.
Steve