later MS-DOS (5.0, 6.22, whatever) will run just fine on 8088/8086/V20/V30 CPUs,

The thing to check is if the current DOS 3.2 on the Epson is really identical to "generic" MS-DOS 3.2... some of the machines from that generation (especially laptops) had some OEM-specific variations in DOS to support certain hardware features.
I guess just try to boot a newer DOS from floppy and see if it sticks :)

I don't think there'd be much point in having a newer version of DOS on that machine.

I want EDIT instead of EDLIN and QBASIC instead of GWBASIC 😀 - if those two (plus any Norton Commander clone) can be run under 3.20, then I'll stick to it. I'll also have to find some suitable utilities (to check disks for bad blocks, to show some system inventory, etc)... I just found out that Windows 2.11 286 will run on an 8086/8088, so that's another lead I'd like to follow.

As for customization, this 3.20 version does indeed come with at least one custom setup utility, that configures for example the serial port's parameters or the "auto off" feature for the LCD panel - I'll have to find a way to preserve that (and see if there are more)...

It's not in your definition of 'ancient', but I found general directory browsing and command launching was noticeably quicker with MSDOS 5 compared to 6.22 on my 286. I don't think the better memory management functions are of any use to 286 and lower machines anyway.

I run a 10MHz V30. I like DR-DOS 7.03 with QRAM 808x memory management, although you need LIM 4.0 EMS memory to really take advantage of it. I also found a way to load DOS into UMB memory by replacing one of the QRAM files with one from a later version of QEMM. I documented it pretty well on vintage-computer.com forums, but nobody really took interest. Using this method, I was able to free up almost 620kb of conventional memory with DOS and drivers loaded into UMB. DR-DOS also natively supports task switching, which is pretty nifty, though that also requires LIM 4.0 EMS.

I only have 640KB of RAM, so I don't have to worry about XMS/EMS/UMB 😀 - I guess my next dilemma will be choosing between MS-DOS 5.0 (for a bit more available RAM) vs. MS-DOS 6.0 (for more disk space using DoubleSpace) 😀...

I just installed MS-DOS 5.0 and started installing Windows 2.11 286 - unfortunately the kit I found is missing the COURA.FON file on the Fonts disk, so the setup was aborted. Even so, Windows does start, but obviously looks incomplete - I'll be looking for another kit, maybe eventually I'll get lucky...

If you are going to use DOS' disk compression, use dos 6.22 with doublespace. Drivespace had some nasty data loss bugs in it.

I'd have thought disk compression on an something as lowly as an XT (or equivalent) would be horrendously slow?

Yeah, personally I think its a bad idea but hey, I know that's never stopped me before 😜

back when the "family computer" was an XT clone with a 20MB HD, my dad installed STACKER for disk compression (that was before DoubleSpace / DriveSpace)... and I actually don't think it had any significant performance impact.
The CPUs in those machines were slow, but so were the hard drives - disk access could frequently be a bottleneck, and in those cases compression could even *help* because you'd be doing less reads/writes.

I'd still probably avoid it (disk errors were harder to detect/fix... plus the driver was just one more thing sitting on a precious piece of your 640KB RAM). But that's just me :)

For now there's plenty of hard-drive space left (~18 megs) - the next step will be to complete the installation of Windows 2.11 (found a 386 version with all the font files there, so I'll copy the missing one on the Fonts disk of the 286 version and try again). Then some utilities, then some games, then some programming tools, then a proper charger, then I'll probably get bored and move to something else 😀...

what you need is MS-DOS/V 6.2 or PC-DOS/V 6.3... I believe it is the newest you can go

I think it is available on MSDN if you have an account... ja_msdos62.exe
unfortunately it is in japanese, but who cares if you know how to use dos?

With necv30 i use pc-dos or dos 6.22 and GEM 3 or Windows 3.0 640x480 256 colors it's a little slow to use paint shop pro. I can to use geoworks 1 but is like a windows 3 for me.

Thanks for the Win 3.0 tip - I searched and found that it still supports 8086/8088 in real mode, so I went for it. So far I have MS-DOS 5.0, Windows 3.0, Volkov Commander and two games (Blockout and World Class Leaderboard - both a pain for the eyes in 4 colour CGA mode on this old LCD, but still playable), and still have almost 13 megs of disk space left 😀.