It all depends on the computer to be modified and it's RAM system. Let's for now focus on the pure RAM expansion issue and drop the part about bank switching, as this is complete machine dependent and a generalized answer, as requested, will be impossible. Even so there are still many hurdles to overcome. One after the other:
Some machines, like original PETs are based on static RAM. They lack any logic to multiplex addresses thus dynamic can't be used as (direct) replacement. Also, no provisions are on board for refresh (*1).
The C16 mentioned above does use dynamic RAM, but with x4 organization (4416 - they are already 64Kib chips anyway :)), so x1 chips can't be used as (direct) replacement. Corresponding 256Kib x4 (4464) chips are available, still the hardware needs the capability to handle the additional address line(s).
Even if a machine, like the 4016 does use x1 chips (4116), it also must provide means to multiplex all 16 address bits, which the 4016 doesn't. Only the 14 lower lines are multiplexed (*2). If at all, a working extension would be using additional 4116, wired in parallel with their CS connected to a small decoder for A14/A15 - and of course only if there is address space available to do so.
The C16 in contrast is already (somewhat) prepared for 64 KiB. The RAM chips can be replaced right away, just A14/A15 have to be supplied to the multiplexers (74257).
Next hardware hurdle is where to put the RAM. Even in a 16KiB machine, the remaining 48KiB address space are neither unused nor free. There is ROM somewhere, I/O and maybe a screen RAM.
The CBM 4000 series for example got it's screen RAM at 8000h followed by I/O and ROM areas. That's the main reason why there never was a 4048.
The C16 in contrast is already prepared to have 64KiB - after all, it's a 264 design, like the plus/4. The address decoder is made to handle full 64 KiB RAM in addition to the ROM and I/O areas. Screen memory is all the way down (*3).
Even if one is able to squeeze in the additional RAM hardware wise, most Software, like BASIC, will not use it. The C16 is again a notable exception, as its BASIC is prepared to work with a full 64KiB RAM.
I did on purpose focus on the machines listed in the original question, as otherwise this would be an endless story. Even when confined to Commodore. But I hope you get the picture.
*1 - Then again, adding static RAM is less work (no multiplexer to considere) and nowadays even for DRAM machines the best choice. Just add it - especially if a suitable expansion bus is available.
*2 - Well, the multiplexer(74153) needed is available on (most) boards, but not wired, so it still be less work to use 4116s or add a new multiplexer on a sub board
*3 - The 264 does show that Commodore enginers where willing to learn. Unlike the C64 which was just a quick hack, the 264 series was planed with extensibility and maximum usage in mind.