Yes, well there is no other way of doing it. The days of starting a ISP out of your house and in a few years be a Sprint is falling away. ISP's will just need to get space from there upstream provider and renumber.
How many times is it reasonable to ask a customer to renumber? Once is certainly reasonable. Twice is questionable. More than that and I would suspect the customer would renumber all right, but as part of shifting to a different ISP.
As many as it takes, This is just something you are going to need to deal with. We started with small blocks and had to renumber several times so far. It is just part of growing, until you are a large NSP connected to all the NAPs you will just need to start will small blocks and renumber over and over until you get /18 or smaller.
This strikes me as being discriminatory against the smaller ISPs. The customers are looking for stability and, from their point of view, being forced to renumber several times along with the ISP is unstable and costly. They'll look to ISPs who will not force them to renumber, the ones with a /18 or smaller already. Do you truly believe there is no way to avoid the forced renumbering problem for the smaller ISPs? -David