I'd probably start by building a time machine.
I never used that as a strategy, but I don't think it's been (very) useful as a strategy for several years.
If you're going to fully develop them all, it can help. In that case, though, now you have several domains that need link popularity instead of just the old one. I'd also take steps to have them owned by different entities, hosted different places, etc.
There are a lots of cases where I own such domains simply because they're worth owning. You'll have to decide if they are worth developing.
