In the 80s, H&K sold 4 half-rack real valve amps, with built-in dummy load and speaker sim.
They are guitar amplifiers, built in miniature. They contain 2 valves each, mostly with pre-amp and output-amp valve stages, and output transformers,
They have many outputs: Speaker, line-level Clean, line-level "Valved", line-level valved+speaker simulation. If you output them into a 4x12, you get a low-power guitar amp,

Crunch Master aka "Blues Master" (EL84, load, spk sim) - Contains an ECC83 and an EL84, run to give crunch, with speaker simulation built-in. 3 eq bands.
Bass Master (EL84, load, no spk sim, gain,tone, master and TMB boosts - Contains an ECC83, and an EL84, clean sounds with no speaker simulator.
Cream Machine (ECC82 "power" tube  + spk sim - The Cream Machine contains an ECC83, and an ECC82 run as a 1W power amp valve. The lowest distortion on this unit is still firmly in Jimi-Hendrix territory.
Metal Shredder aka "Metal Master" (no power tube or load; has spk sim) - The Metal Master has no output valve, but it uses two ECC83s to get an 80s rock sound  (speaker simulation built-in). 3 eq bands

My question is:
Can similar units be built economically? e.g. a DZ30 preamp, with a single-ended one-EL84 output valve, run at a much lower level than normal.
there would be a massive saving on transformer and power valve costs. I assume a basic sag simulator could be included

At present all the low-power amps I own have very basic preamps. They are either 50s retro or 2 tube models. (one ECC83, one el84 usually).
I've had 2 upgraded with tube rectifiers, and bias tweaks, new OT, etc. I even had one BH5 set up with a mix between el84 and 6L6, that sounds good!

However, these all have quite basic preamps.

Could I not have an amp with a DZ30 preamp, or a BM HRM preamp and a basic class A 5w power amp?

Can Nik make a modern, better speaker sim