Build a tool for generating leads from LinkedIn profiles

I’m a technical person (developer), not a sales or marketing guy, and I’m trying to figure out if a dataset I can generate is actually valuable. I discovered a way to collect LinkedIn profiles of decision-makers who have used a specific service. Example: Imagine you run a marketing agency. I could give you a list of LinkedIn profiles of decision-makers **in your city** who have previously worked with other marketing agencies. The idea is that these people have already shown intent (they hired a marketing agency before) so they might be good prospects for competitors. Before I spend time building something around this, I’d love feedback from people who actually work in sales or lead generation. A few questions (a lot of them but answering even one would be very helpfu): 1. How useful would this type of data actually be? Would sales teams care about leads like this? 2. How hard would it realistically be to sell something like this? 3. What would be the best way to package it? Would you buy it as: a CSV lead list a subscription database or a SaaS product around it? 4. What type of businesses would value this the most? 5. If you were to pay a subscription for similar idea to mine, how many fresh leads you expect to find every day/week/month? (Sorry I don't have an idea about how this works) Marketing agencies are just an example, maybe there are better industries where this would be more useful (please let me know if you can think of good/better ones). Curious to hear honest feedback from people who actually buy or use leads