Just a FYI in regards to:
"... Secondly, if the BLM-1 runs out of juice, you can't use an off-the-shelf battery to get you through the day. ..."
True there's not an direct off-the-shelf battery, but there is the Olympus Battery Holder (PS-LBH1 W) which takes three CR 123A batteries.
Have one as a backup for E-500 and C-8080.