2nd ISP and BGP question

Hi,

We are a small team (two members) and maintaining 8 core sites in a VPLS network. We currently have single Internet access at site A and planning to get a second one at site B. We do not have BGP at this point, but once we get the site B internet access, we are planning to do BGP with the provider and implement iBGP internally.

Site B Internet bandwidth will be half of site A. To prevent asynchronous routing we are planning to prepend our ASN at site B since site A has a faster speed we will keep it as the primary. Eventually, we are going to upgrade site B speed if the network demands it. For now, just half.

1. The question that I have is, is our plan make sense?
2. Should we utilize site B for something else other than keeping it idle until site A goes down?
3. Instead of keeping the site B Internet access idle, what would be a good use case to make good use of this?
4. Once we get to the point of getting the same speed as site A what would be the best approach?

Thanks