Carnival, eh? I have friend in Liege, and her correspondence of last year confirms your excuse as legit.
I find that combat encounters I run seem more "genuine" if I've spent some time "fighting it out" in my head.
I have an encounter in mind, but I don't necessarily want it to be a static opponent, so I try to think about what they are doing, what their objectives are, and what might be happening "behind" their scene (like orders from their command structure or their general morale).
Perhaps a light infantry squad has been sent specifically to hunt enemy (PC) armour or armour support units. They are scouting, hunting, skulking, and preying, things that the PCs may themselves be doing. Opposed Stealth Tests (both the PCs and their opponents are crawling slowly through undergrowth or rubble), Awareness or Per Tests to note the sounds of a vehicle motor or Walker drive pistons above background noise (or above the thud in a PC's ear of his own fearfully pounding heart), possibly Navigate Surface Tests to pinpoint the enemy's direction (sounds echo, making it difficult to be precise); these are the kinds of things I would think about, and knowing my Players I have an general idea of how they will respond/react/behave to the encounter, and can "plan" their opponents' responses/reactions/behaviors accordingly. Equipment and gear can be used by opponents as well as PCs; the "bad guys" are less likely to be surprised if one of their unit is operating an auspex…
I also try to consider spacing (we use tactical maps); it's important for the GM to have an idea of how he spaces the PCs' opponents, as well as the general spacing/formation the PCs have adopted. Then decide whether you want the enemy to "bull rush" the PCs, stagger their advance and cover with supporting fire, "dig in"and deny the PCs' advance, or tuck into concealment and let the PCs pass and then follow/ambush them. Are the opponents brutal (meaning they kill all enemies to a man) or are they willing (or ordered) to take prisoners? Are they stalwart combatants, or will they flee when half or more of their number are severely wounded/slain? But what to do if the PCs notice an ambush? Play out the enemy's adapting combat responses in your head (based on their doctrines/morale/orders). Not everything will follow these in-head playouts precisely (as GMs, we all know Players have a knack of carrying an extra monkey wrench or three), but it's better to have some ideas organized ahead of time than it is to be winging every detail on the fly.
It is far more enjoyable for the Players and the GM to consider these things, and to spend a bit more time preparing for encounters than that simply needed to write down "Bad guys with guns attack PCs, 1 Missile Launcher if needed."