Love this idea, but I think it would need some very specific map designs and/or changes and different impediments than 'mooks on patrol' or 'devices'.
Really, setting up the basis of this mission type should fill in detailz -
why are surveiling this person (is this a shakehands for a character on a power play theyre running with someone else? Is this an actual transaction? Is this a torrid illicit romance that the VIP is keeping a lid on because husband and megacorp shares hang in the balance?)
Where? I instantly perked up about this idea because it could allow more 'public' mission venues, like a rave or club, where catching VIP letting their 4 inch pump with knife in the heel playfully dangle in front of the object of their affection in the VIP booth is the thing to catch and observed over time as it gets flirtier and flirtier with each turn. Thats an option to maybe develop but observing transactions and associations can be done on current maps with entry exit points, for sure.
How? So in a lot of movies and games, surveliance is not static, its protag following target through public venue and trying to not lose observation so that you can eventually make their associate and get even luckier with the content of their interaction. It might be hell to make, but surveiling success could be layered with 'made where they went', 'made who the met with', 'made what they did', 'made the composition of what they did'(oooh lala if we are talking our hot lady boss stepping out on her husband), but these can be reward intervals perhapz