My experience with this on SAMP (at least gangs):
1. You'd start to investigate a gang, everything would be cool, you'd get some members identified, maybe do a drug bust.
2. You'd want more, start surveillance on key members. Oh they have wallhacks? Well they won't be doing anything while you're there.
3. You'd want to do an arrest or some sort of a search or gang enforcement or anything. Well, there's a problem. The guy you're after is online but your fellow gang detectives are offline. So you have to beg people, do a briefing so it's realistic etc. In the mean time, the guy went in his house to AFK or offline. Better luck next time.
4. You want to investigate how the gang works, who runs what etc. You would realistically need a snitch. Well, let me tell ya, these gangstas in Jefferson DO NOT be snitchin. They'll do time (10 hours max), they don't give no fucks cuhz....
5. You somehow manage to get a snitch by encountering a good Role Player who is not scared to sacrifice his character (usually those with little to nothing to lose a.k.a outsiders or some sort of a lower rank) and you finally manage to identify the leader. Well, let me tell ya, that leader kinda prefers Role Playing on an alt that is insider so he can shoot, sell drugs, Role Play with lower ranks who are in the majority, the fun stuff. So you can barely EVER catch him online, let alone get a team up (as, at least during my tenure as gang detectives lead, you'd have 5-7 active detectives AT BEST).
6. You fall into this circle of essentially doing gang enforcement work instead of actual detective work. You pat down people that you think may be selling drugs after observing them and pray to God they don't have wallhacks.
Bonus facts:
1. It is virtually impossible to actively follow someone somewhere. You will get spotted 10/10 times due to lack of regular traffic, even on a SAMP map that is far smaller than GTA V.
2. If the character you are after has anything of value on him or is in a crowd of 4 or more people, you are almost always ending up in a shootout so you better come prepared. This was the case for everyone, even those regarded as elite Role Players (even some ex members of FT).
3. Punish dumb behavior (for example during gang injunctions people would just not fucking go inside and RP but keep at it like nothing happened) by taking it IC (as you're not an admin) and you'll be called names, you'll be called arrest hungry, shootout hungry, robocop etc.
4. A gang is getting more violent or is involved in drug trade on a larger scale, you get the info about it and decide to give them a bit more intention, you're automatically "not letting them create RP" or "not letting them RP in their hood" and it is frowned upon.
In conclusion, anything you do will be judged and aside from everything being very hard to organize even for simple things such as shakedowns and such, it's just not worth it unless you have A LOT of free time. Otherwise it will be just mediocre, you will fall into gang enforcement and not do any real investigative work. Also paperwork was awful lol, you'd spend hours writing a casefile just for you or the person you wrote it on to be PK'd out of it.
But maybe something can be done. Thoughts @danielswe @Redz ?