Not in particular, but your topic did give a brief burst of inspiration, I think I'm going to work on some homebrew rules for Greater Attunement. This will add/modify some items to be able to devote multiple attunement slots to achieve greater effects. For example, a Flametongue might give access to new spells, a strength-based ranged fire attack, or fire absorption. The only real hangups I forsee are that there's not reason not to double attune (or triple, if I put those in) unless there are other items competing for attunement as well, which would be an issue in low magic or low level campaigns.