Seeing there is a Team Death Match mode before HECU vs Scientist, I am hoping for a mission similar to CS or TF. Even though I know BM 
M is very fast pace to have missions, I still want to suggest it to get it out of my mind.
Objective type 1
So the science team will try to reach an objective and activate it(Example: Signal for SOS/Rocket), while the HECU will stop them from it. The game ends when Science teams success or they run out of time which is HECU’s victory.
Or the HECU will tries to set a bomb to destroy evidences and the Science team must stop them from doing so.
Objective type 2(Insurgency inspired)
Multiple objective, science team will restore powers, fix the energy or such. With HECU team trying to stop them, if time run out, the HECU team wins or if the Science team success, they go into next stage with more spawn. And they will need to find a console to activate a blast door, note: They will need to hold the place for a minute. Then they will try escape the Black Mesa with the tram right.
This is pretty much how much I can type out with my sleepiness and shoulder pain.