You can easily hide the motor by glueing in a piece of black paper in an arch capped at each end with a piece of paper. I actually using liquid Supa Glue cover all the paper on both sides thus giving it some strength, kinda like adding resin to glass fibre. It's best to paint the top side with the Supa Glue, form the required arch and glue the end pieces of paper. Trim the ends when dry and then glue the paper arch into the interior and finish off coating the inside of the arch with glue. Finally the excess paper will cut cleanly with a hobby knife due to the glue making it hard. As you said it's personal choice in these things. Myself I don't like the motor to be visible and this is an effective way to hide it that isn't as costly as using plastic sheet which would also require painting. The glue gives the paper a sheen very close to the plastic too
I did same thing but took thin styrene sheet plastic from ever green and made a new interior bottom and a raised area for motor and looks a million times better can't see motor in the interior
I have 2 of these. And yeah they are a novelty car at best....handling is not their forte....this looks good.........wider axle/rear tires might look weird but would also help.