It's a fair jump from 700c to 26".
I would be concerned the assistance would stop at a too low real speed, unless you can derestrict the bike.
Also bear in mind the motor and pedals will be closer to the ground, and you will under gear the bike.
Fine for steady road and cycle path use, but the pedals might ground under hard cornering or on a mountain bike trail.
So if I used a deeper and wider tyre on a 26" wheel it would compensate the loss of diameter in wheel size.
A mate of mine changed a skinny tyred 700c to a podgy tyred 650b.
The circumferences were close to identical.