keep in mind that *existing software* is also a metric in my consideration.
Oh. Well in that case, I think you're screwed. Most of the 68k systems of that era (or at least most of the ones that have had any software preserved) has highly proprietary operating systems that were heavily dependent on "elegant" but proprietary custom hardware. (I'm thinking of Amiga, Macintosh, and the early unix workstations (SUN-1 !))
Go with the 8088 (or get a NEC V-20, for some near additional capabilities and nearly identical hardware.) No need for an 8087 (I'm not sure why you included that, since the 68k doesn't have an FPU.) MSDOS and the PC BIOS are at least designed for portability across "similar" hardware, and there has been continued development of things like FreeDOS.
Other possibilities for retro-computing with some hope of running old software include a Z80 running CP/M or a 6809 running OS-9. (I'm particularly fond of this recent 4-chip Z80 hardware:
https://hackaday.io/project/19000-a-4-4ics-z80-homemade-computer-on-breadboard - it's been made to work by several people in several formats, and is currently running CP/M, and Forth, and "ROM" BASIC. The basic design might work for other CPUs, too...) (Hmm. There was an OS-9 for 68k; I'm not sure if it ever got much traction...)
6502 has similar problems to 68k - popular software (C64, Apple ][, Atari) was dependent on custom hardware. In general, when you look at classic personal computers, there was a LOT of custom hardware, and most of the "really clever" programming came from manipulating that hardware, rather than being generic xx-cpu software. (It's a bit depressing.)
(Keeping in mind that while most of that "personal computer revolution" was happening, I was off programming mainframes and not paying THAT much attention. But that's how I remember things...)