I'm not hassling you, I'm asking you relevant questions. Why do you think this doesn't exist yet, at least in a way you know about it? I don't know your context but you do so I can't answer. The answer cannot be that you are the first person to consider the initiative. So seriously, why?
You could contact the most relevant local organizations and ask them if they have such a structure. If Yes, ask if you can join or help. If No, ask why.
Infiltrated isn't even a question. What you describe would be de facto public and open to all.
How could reports be vetted? Call ICE to ask? Minimum number of reports? Lawyer substantiating?
Assuming you could get 100% accurate information perfectly vetted, what action would be taken on this basis? You thinking a flying squad? Armed self defense? The entire neighborhood fleeing? Lob water balloons full of paint?
collect all the testimony for the record. so that nobody can say otherwise.