Longish story, but I wasn't able to test the capacitor-on-R48 theory. That leads to the rest of the story. So just yesterday morning, I decided to order a junk battery from Amazon. Then, later in the day, cleaning out the garage, I found a defunct scooter 36 cell battery pack...it was working, but something went wrong with the electronics (the BMS). The batteries are bone fide CHY18650 2500mah Lipos and seemed to have good charge/discharge properties. I decided to scavenge 6 of them and do a full rebuild of the Dyson pack. After various bits of chopping nickel strips and slicing my fingers, I got the batteries out and in, and then needed to reconnect the R48 resistor back to the 4.2V power tab (P2). Well, it didn't work. I thought the surface mount resistors were kinda robust, but not against my clunker soldering iron. R48 opened. My last chance bit of luck was to find an old-fashioned 220ohm 1/4w resistor in some old potted electronics board. After chiseling it out and tack soldering it in (replacing R48), the pack actually worked (that is one robust resistor).
The refurbed pack did a 15 minute run, which seems pretty good. The board reprogramming is great, letting me know all is well at charge and at low battery discharge. Stayed pretty cool (maybe 100 deg at the end of the run). I think it's good!
Now I need to deal with the extra junk battery I ordered. Very cheap ($23 with 2 filters...maybe $14 after accounting for not needing to buy 2 filters). We'll see.
What I can't tell is if the install of the 220ohm resistor (vs the original 1K) might have solved the power-up sleep problem without the need for the capacitor filter. I'm not prepared to do additional research at this time...
Thanks for this thread, and especially to tinfever for the help and advice.