Apply for another credit card, such as The Nest. Reallocate your credit limit to put maximum amount on The Nest, minimum amount ($1,000) on SPG. Cancel SPG. Reapply. Change billing date. Reallocate limit to fit actual usage.
Good idea in theory, but reallocation isn't automatically granted, as I found out. I'm about $8K from topping out my credit limit on my Starwood card. A couple of months ago I tried to move $8K LOC from my Hilton card to my Starwood card - Amex turned me down. And I always pay off my balances in full. If I was able to move most of the LOC to the Hilton card, get a new Starwood card, and them have Amex turn down my reallocation request, I would not be happy. I have enough Hilton points to last for awhile, but you can never have enough Starpoints.
As for the Nest, it might be worthwhile if the MR cards don't see another double points promotion for a long time, like we had from 09/05 through 12/06. $15K gets 60K Hilton points (first year) or 15K Starpoints - if I needed Hilton points, I might take you up on the idea.