Any business needs: 1. to be able to change upstream providers without having to renumber.
Why not just keep it easy to renumber. It's only hard to renumber if you make it that way.
2. to be able to change access providers without having to suffer multi-month down-times.
If your company relies on your access, you need more than one provider. You can easily dual number every server you have. That way, if you lose one provider, change DNS a bit and use just the other. You can then renumber the other side of the dual numbering at your leisure with a new ISP.
3. to be able to have its net-block(s) visible regardless of which ISPs they are currently using.
Design to renumber. If you need reliability, get two of everything. It's really almost that simple. DS