So i want to give the IP of ISP 1 to Tenant 1. But when they surf i want them to pass through ISP 2.
The maximum you can get is that you give ISP1 addresses and dst-nat rules for incoming connections to tenants who want to run servers locally, but you use ISP2's addresses for src-nat. So instead of determining their public IP autonomously, the tenants will have to configure it manually (because outgoing requests will use ISP2, so all those "what's my IP" services will show that one).
Another way could be that you would order your own public IP range and agree with the ISPs to talk BGP to you. This way you would advertise that IP range to the world via both ISPs using BGP, preferring the one with better bandwidth.
Yet another way would be to run a VM somewhere in a datacenter and a tunnel from there, but that causes either MTU problems or bandwidth issues if you hide the fact of fragmentation from the users. And in DCs it is usually also not easy to get multiple public IPs for a single VM.