That, or just plug in an old VGA card with good legacy VBE/VGA/EGA support in a PCI slot (with a PCIe to PCI adapter if necessary) and pass that card through to the DOS VM. 🙂 You could even keep your shiny modern TFT monitor connected to your primary modern graphics card and hook an old CRT monitor up to the old card.
But you're right, legacy VGA emulation is already fairly well implemented by most popular hypervisors, and would be much more practical. Maybe I was overly worried about the result being perceived as less "native" somehow. Particularly the lack of true text mode support. But then again, in the case of games, who cares about that?
So focusing on DOS: if someone savvy enough would either port the sound card emulation code from DOSBox to QEMU or VirtualBox OSE, or alternatively implemented support for a physical OPLxLPT device on the host as a backend for the FM-part of the emulated Sound Blaster card, we'd be pretty much set, wouldn't we?
I mean, it will still be awesome to get classic ISA sound cards to work properly in modern systems that were never designed to accommodate them, but it would no longer be the only solution for people wanting to play DOS games (particularly the more demanding ones from the DOS extender era in the latter half of the '90s) natively on newer hardware, right?