As much as I like the idea of a Virus 'trial run', Brzk's assassination was just that, an plain old, everyday, vanilla assassination.
Brzk's death was the result of two distinct Megatraveller metagame aspects coming together. The first metagame artifact was the belated attempt to find a way to end the Rebellion. The second metagame aspect was the increased interest in running 'high powered' campaigns. Let me explain the second one in more detail.
Skill wise, the original CT chargens were good for the 1970s. However as RPGs grew, the skill-poor nature of CT characters became apparent. Consequently, expanded chargens were developed and characters with many more skills appeared. Having more skills is a necessary part of 'high powered' role playing.
Next, just as there was an interest in post-apocolyptic settings during the mid to late 80s, there was an interest in espionage/covert operations campaigns and settings. Traveller got into the 'sooper' spy, 'sekret' agent, Jethro Bodine 'Double Naught' wannabe dreck with the introduction of IRIS. (He hadn't done anything else, Dave Nilsen's masterful deconstruction and decanonization of IRIS ranks him among the greats.) The idea of IRIS saw many imitators, among them Tukera's Vemene and a group belonging to Mendares, a Julian Protectorate megacorp. IIRC, the Mendares groups was called 'Transtar' but I am most likely wrong.
The Mendares organization, which had a hand-in-glove working relationship with whatever official intel groups the Protectorate fielded, was featured in several adventures in both GDW's Challenge and DGP's various magazines. One adventure involved foiling a plot to kill Archduke Brzk. That adventure even detailed Brzk's orbital palace, the same structure that later blew up.
So, in Brzk's assasination, we see a several metagame and story threads come together. We see the first faction in the Rebellion that fails; a necessity if we are to end the Rebellion somehow, we see a tie-in to all the published Mendares' 'spook group' adventures, and we see another example of 'high power' espionage/covert operation leanings RGPs had at the time.
A 'Trinity' test of Virus would be nice, but it doesn't quite fit in the OTU. Once released, Virus cannot be put back in the bottle. Virus used to destroy Brzk's orbital palace is also Virus released to infect the Antares system, the subsector, the sector, and eventually all of Chartered Space.
Those who dd 'off' Brzk may have used a 'virus' or 'virii' for the job, but they didn't use Virus.
Have fun,
Bill