Ron,
My “simple” suggestion is nothing new. Wire the playback head out to connectors and add an external preamp.
However, let’s discuss some fine print.
Where to mount the preamp? You could check with others like Mike L. to see how he/they did it – from pics it appears that his pre is on the floor next to his left-hand deck (on Stillpoints!).
I did wire out two A812’s and mounted my pre directly to the cowling on the underside of the transport mechanism. Found I could drop the wires from the headblock “straight down” and into the pre through a hole drilled in the cowling. This got the total cable length down to no more than 18”. Another possibility is to get a shelf or table under the transport to support the preamp and bring the head cables out the same way.
Other considerations – do you ever consider recording with the deck? If so, you might want to have a switch added to the headblock that switches the output of the PB head to either the internal or external electronics. This can allow the meters to work on playback, with no other modifications. On the decks I converted, I did tap the output of my pre and feed it to the meter electronics in the bridge thru an added selector switch so you could monitor the level of either playback “choice”. However, with switching the head output you've added an additional "impediment?" for those “tiny signals”. Though I’ve never heard of a problem from those who have done it.
For a long while, there have been a number of threads relating to “improved” electronics, either on-card modifications or via whole new cards. There is a thread right now on Audionirvana relating to the A80. I don’t know how one “vouches for” the sonic results of any of these. From my own experience: like what ML did for the A80, any “improvements” should include both the reproduction AND attendant power supply circuitry.
THANKS and best wishes navigating your journey. Fortunately there are a number of folks who have made it to a safe and worthwhile landing!
Charles