I don't think that will work, db3l. Your block of IPs is routed through your main IP -- if you disable it, you'll lose IPv6 connectivity.
Hmm, are you sure? I just manually deleted the auto-configured address on one of my Linodes, added an address from my local 4096-address pool and it works fine. Though there are some differences between the 4096-address pool and a /56.
The 4096-address pools work through neighbor solicitation, so shouldn't have any dependency on other addresses. That's also why you can assign addresses from those pools arbitrarily to any Linode.
If you've also requested a /56 it does have to be explicitly routed through some other address. So if you chose an auto-configured address for that purpose then yes, it has to remain active, so avoiding it for outbound traffic probably requires the deprecation approach. But what I did for my /56, and what I think is more flexible, is to route the /56 through an address from the 4096-address pool. That way, your /56 will automatically route to whatever Linode you choose to assign that pool address and avoids any hardcoded dependency on a specific Linode.