Test API, Dynamic Threads

I want test an API.

My scenario:

• 1 hour.
• From 0 to 300, 000 users.
• 3 request by user.
• Users (threads) increments by second, like +5, +15, +20, +5, +30.
• threads are remove also, -2, -5, -15, -5.
• When the threads is alive, call again the 3 requests every 20 seconds for example.

You know some aplications for this or a better for to simulate this, i mada a little tests with JMeter, SoapUI, and Locust IO but it's not what I'm looking for.