"One thing that always amuses me is the fascination with magnetising the joints and removing the battery box these days.

None of my venerable H/L tanks have had this.
Screws and the battery box are the order of the day.
If I need to get into the hulls of these things, screws are not really hard to get out and theres a solid reason for doing so.
Also, changing batteries is much easier or, at least present similar difficulties to cracking the hull to do so.
The Taigens I have are a PITA to change batteries(not the JS2) as the way I have completed the outside presents a problem with skirts, tow cables and suchlike.
On the flipside, manipulating a model to access the underslung battery box cover, change the battery, and reinstate the cover is also an issue in itself at times.
As I am probably an expert in bringing total wrecks back to life, the screwed hull and battery box is a go"
Thanks for your contribution Herman Bix.
EASY ACCESS BATTERY.
Being able to access the battery easily is essential if the tank is going to be run regularly - unless it has a charge socket that is easily reached from the outside of the tank.
I am not a fan of having the battery buried inside the tank if it cannot be accessed easily and quickly (especially with the use of LiPo batteries) and I would rather remove the battery to charge it than use a charging socket to charge it inside the tank.
It would be much better if it were possible to access the battery without either having to turn the tank over to access the battery box cover underneath, OR to pull the top half of the tank off after the battery has been relocated inside the hull.
None of the above three options is a "perfect" solution in my opinion.
BATTERY IN TURRET - a perfect solution?
A compromise of having the battery located in the turret is perhaps the lesser of the evils if the turret top can be easily removed (such as on the Tamiya Leopard 2A6) and if the turret has enough space to house a battery . Modern MTB's usually have larger turrets than their predecessors and so it can be easier to squeeze a drive battery inside it.
Even this "solution" is not perfect or as easy to achieve as I discovered when making this conversion to my Heng Long Leopard 2A6! Converting the turret top to be a "quick change" (but secure) fixing was easy and the magnets are a much better way of holding it on than all the self tapping screws that it came with...but the main gun pivot axle is secured by a pair of "half-clamps" that are moulded into the top half of the turret !
The gun elevation unit is also held into the top half of the turret moulding, so that will need relocating (or replacing with a servo), and with the "half clamps" cut away from the turret top moulding and fixed onto the lower halves of the bearing clamps, both can be mounted onto the turret floor so that when the top is lifted off to change the battery, everything stays in place and does not need any fiddly realignments to put it all back together again .....like it does now.
BATTERY BOX.
Having the battery fitted in its "box" underneath the tank does not impress me too much.
With the weight of the battery only being held into the tank by a single self tapping screw, this is not a fixing that makes me feel comfortable that it is a secure long term way of holding the battery into the tank. Only the one self tapping screw prevents the battery from dropping onto the ground if the self-tapped thread in the plastic hull should fail.
Repeatedly screwing in (and unscrewing) the single self tapping screw into the moulded plastic hull is not a good well engineered solution that I would be happy to rely on in a tank that will have plenty use and battery changes. With repeated battery changes the self tapping screw is bound to eventually chew its way into the plastic until its becomes a loose fit and no longer able to hold the weight of the battery in the tank.
Another worry for me with having the drive battery underneath the hull is that it will not be protected from the ingress of water as the battery box has no gaskets or seals . This is not a problem if you have no intention of ever driving the tank outside in wet weather or mud....... but I like to keep my options open!
BATTERY SIZE.
Another problem with having the battery in a close fitting box underneath the hull is that it determines the maximum size of battery that can be fitted into the tank. My T90 came with a small "half-sized" main drive battery, and the box that it fits into is not big enough to take a more "normal" size of battery.
Fortunately (?) my Heng Long Leopard 2A6 and my Heng Long Challenger 2 were both also supplied with this same "half size" battery, (rattling about in the "normal size battery boxes), so I have three of them that I can rotate, but the longer term solution will be to relocate the battery - probably in the hull as the T90 turret may not be big enough to take a "normal" sized battery..
The weight of this half size battery is minimal and so the self tapping screw that holds the lid onto the battery box has a lot less work to do to support the battery weight - but the lid is not "sealed" and it is still only secured by a self-tapping screw, so in the longer term I need to change it.