I would also really like a more dressed down pure Staking wallet that could run on the PI2 nav wallet is kind of a recouces hog.
(PI2 would allow people to keep it staking 24/7)
For a Pos coin Imo you cant really go lower then 12% a year if u want to keep people motivated to keep staking.
I have no direct experience with Raspberry or other stake-box, but it is interesting
theme to explore.
I guess you are referring to the version of the wallet without the QT GUI, right?
Unfortunately I think the heaviness at runtime, is an indirect effect of the
large number of blocks that are in the block chain now.
IMHO, to solve this problem, it could take a deep rewriting of the architecture
of the wallet, a work of high engineering.
PS:
Maybe the new Odroid XU4, having the double of memory than RPI2 could be a better choice.