That's basically already a thing. There's a big market for older riders who want a little bit of discreet assistance on their group ride.

https://www.orbea.com/us-en/ebikes/road/gain/

To my eyes, that bike obviously has a battery in the downtube. But I'm not the average person where bikes are concerned so perhaps I should have said, "a bike that would fool other bicyclists."

Assuming the pros are cheating, the professional assistance is unlikely to be of use to a regular human. At the professional level, a 1% gain could be huge, whereas a normal rider could gain far more than that by better techniques/breathing/equipment/whatever.

It’s not 1% it’s 35 watts. Which matters a lot more when you’re a rider who can only put out 200 watts.