If contacts highlighted in the photo above are removed, rail power pick-ups are isolated from the loco frame. There is a remote possibility that derailment or some other accident could somehow short the frame through rail contact, but it is very unlikely given the construction of this model. In other words, there is negligible risk leaving motor terminals connected to chassis half-frames so long as the chassis is disconnected from rail pick-up.
A single screw holds the tender together, but it's center screw mounting must be removed to open space for electronic components. As a result, we need an alternative method for reassembly. The new arrangement holds the base with tabs added at the left end in the photo and, on the right, screws into styrene blocks glued at the loco end of the tender shell.
Miniature plugs and sockets allow the tender to be disconnected from the engine but the effort is not convenient and should rarely be necessary. I replaced plastic wheels on tender trucks with metal and considered adding wipers for power pick-up. However, wheel wipers on the loco drivers are nicely engineered and likely to be more reliable, justifying the extra wires between engine and tender.