I'd be very careful here. HSM has matured, but I used to use it in an imaging solution and it was sssssllloooowwwww at times looking for old images. Not sure how the query processor will deal with this.
I think burthold has the best solution and we used to do something similar. We built 3 dbs, one for real time (usually 1 yr), another for near, which was a slower server, but had another couple years worth of data and a 3rd older server with everything else. We used views and stored procedures (nd linked servers) to check if you wanted old data and then Unioned the queries from other linked servers if we neede them. With SQL 2000 and federated Database servers you could do the same thing.
Steve Jones