I Was involved with creating a platform such as this and i have another SaaS platform that has been operating for 3 years.
Do NOT underestimate the power of Customer Service. You will need at least one or two agents on the phone at all times to deal with training, complaints and issues.
On the influencer marketing side, there are many many competitors out there on both the data side, campaign side and recruitment side. Make sure you research them all and have something over them if you can.
A great website to see a bunch of competitors and platforms is https://www.g2crowd.com/
I also recommend using AWS to be able to scale effectively even though the cost can be slightly higher than hosting on normal servers. You will need a DevOps guy to manage this effectively.
Feel free to message me if you would like to talk more on it.