Well, it's mostly due to me liking the VGO by itself due to it's high ROF/beefy sound effect, but having your IS upgraded with 2xVK does eliminate their primary weakness of getting rushed by more CQC oriented squads like Fusiliers/MP40 volks/assgren etc.They'll lose in return long range against Obers/vetted LMG grens but mid range it's a very even fight, and you'll dominate both of these squads close range.
When I use the SWR commander I like to build 4xIS, and by the time I get the M3 halftrack I have like 170-250muni approximately in reserve to upgrade them with at about the 7-10minute mark depending on my CP situation.
They can go toe to toe with feuersturm MP40 volks/early pzgrens whilst beating them at mid-long range.
I'll give you the benefit of the doubt and not gonna say that it is outright bad. I definitely can see the advantage, but only if you skip the weapon rack. Otherwise a vickers is almost 1.4 more expensive then a bren, while Brens have better synergy. Perhaps it is viable in 1v1, not gonna argue about that, since I don't play UKF in 1v1. Also, tightrope always tries something new and sometimes it sticks (like AssSection spam), but sometimes it does not, like countless other niche strats he tried.
But again, maybe this strat viable, but I lean towards "no" in a sweaty tryhard situation.