People who play MP missions, are, in general, phillistines. They are not interested in plot, character or atmosphere - they just want to hide in bushes. Cutscenes interfere with their ability to hide in bushes - or indeed run around not hiding in bushes, depending upon their style of play - which is what makes them unpopular.
Either pander to people who wish to enjoy OFP to the full extent of its capability by including extensive cutscenes in MP missions, or pander to people who wish to gain pleasure by playing OFP while simultaneously excluding from their universe many of the best aspects of the game by not having cutscenes. The former will allow you to gain respect from connoisseurs of the game like me, and the latter will mean that your mission will be played by the masses.
Choose.
There is however a technical point equally applicable to SP and MP, connoiseurs and morons alike. It is tedious to have to sit through a cutscene which you have seen before. Since Intros can be skipped, and cutscenes cannot, it is generally desirable that "initial cutscenes" be done as Intros rather than cutscenes in the mission.
In addition, an opening cutscene is usually a bad idea in terms of the pacing of the the mission: you have had all the delays and background of getting the mission started, and when it starts you want it actually to start: at that point a cutscene is frequently sub-optimal. Getting the mission and Briefing is Slow, so now you want Fast. In other words, don't do opening cutscenes: put it in the Intro and Briefing.