Haven't done it , but i have learned that its best to invest in best battery and higher power ( not 33v , 44volt or above)
But I do think it would be cool to do, for example power assist would be a great way to put step thru / ladies, vintage bikes into everyday use again : lots of room to attach components
-There is online e bike kit conversion company who claims to have the best battery technology , and can provide a turn key front wheel drive to whatever wheel spec you need ......they lace their machinery to standard wheel sizes and send you the whole wheel....... with a turn key controller ..... (this avoids a rear wheel chain involvement) sorry i dont have the name now .... but they are unique because run like a tech start up ......and quality convenience focused , visible / transparent .......not a sketchy ebay kit with no customer service, or way to reach them again.
of course that's not so gonna look so period authentic, so you will might lean toward lacing a generator/drive hub to your prewar rim
At one time I did attemt to repair / replace a modern eZIP ebike which needed parts replaced and a charger ...... tracking down the original parts was a nightmare ........... ended up with a PO box and a third party working out of a storage unit who spoke no English ......so i learned .....not all ebay/ amazon kits are worth buying , if you pursue , i would recommend researching best battery and component reliability reviews ......
i see lots of people selling there non working ebike projects : "needs works / needs a new battery or no charger ... etc etc ... " folks I have spoken to emphasize not trying low power/underpowered setups that atre a cheaper price point.
(in the same manner as obsolete power tools .... when battery fails its not cost effective to replace ..... )
I too would Love to see someone who has done it post theirs !