I have just added PD notifs to the Ginabot notification service roadmap for you.
I think 4 weeks is perfectly balanced and no need to go lower, if we are worried about exchanges voting we can add an exchange blacklist/oracle that prevents known exchange accounts from voting.
I iike the incremental pd idea over 4 weeks, starting low and increasing but I'm going for the simplest method with least code for this HF which is just a parameter change from 13 to 4 weeks, we can go fancy on next HF if needed.
I can facilitate trezor support, will require proposal approval of 20K USD to list steem on shapeshift, then Exodus wallet can integrate and finally, trezor can support steem with a bit of development cost.
RE: HF Proposal: Vote to Reduce Power Down Period to 4 Weeks