When I do conversions of small plastic models to RC, I generally consider the models to be "semi-disposable".
I find that plastic models have a limited life, as a rule-- sooner or later, they get banged up, pieces get broken, etc. So I don't build them like I would a larger model. Of course, some last longer than others of course-- I've got a Lindberg tug that I've run for about 15 years.
My opinion is that radios and batteries are so cheap these days, that I just build them into the model-- I don't worry about providing access to the interior for regular maintenance-- it just isn't worth the trouble.
On my Lindberg tug, for example, I installed and thoroughly tested the running gear and control system, taping the deck in place until I was sure all was working reliably. Then, I glued the deck to the hull with clear caulking, which gave me a nice watertight bond, but one that can be cut away if needed. I then made a small access hatch in the superstructure to give access to the radio on/off sitch and the charging jack.
In the last 15 years, I've had to remove the deck exactly twice. Once, to replace a worn our universal, and the other time to replace the original nicads, which eventually wore out and wouldn't hold much of charge.
Just a thought......