I think this isn't so much an engineering problem as one involving human psychology.
The devil in me would suggest fitting a nice turntable with a variable speed function so that the customer could set it to suit their taste
A Garrard 301 or 401 would need space for an arm so there might not be room, but was the HF4 variable speed?
I guess an external turntable wouldn't be acceptable, so that rules out the Transcriptors hydraulic reference and the LP12+Lingo.
Should be fun when they see the prices.
Seriously, If it's not a bad case of golden memory syndrome (I suspect it last played long before the era of smartphones and MP3s), I think they were used to hearing the thing playing slower with it partially seized with thickening grease. Possible ways back would be re-greasing with something like Rocol Kilopoise or adding a weight to simulate an autochanger stack full loading the bearing.
David