First problem, tubes aren't made anymore or it will be chinese ones...
Secondly energy consumption will be a lot more, not in the green interest....
Third, cost, any design going back to tubes see point 1 will be horrendous expensive.
If you want all the modern goodies like DSP forget it, tubes cannot replace the processors used for that.
You could go for a hybrid where audio and P.A is tube rest is modern.
Though good designed FET P.A.'s now come to a stage they can be just as good as tube, if you are ready to pay top prices that is.
So, looking back at the tube era it was nice and we remember the good parts, but forget how unstable they could be, my FT991A is 0.5 ppm on frequency... try that with tubes, and no stabilising with modern methods.
You would need a very big battery in your car to feed the 12 volt to 110 volt 60 Hz converter.
All in all very unpractical, even modern cars thaat "look" like the old ones are build with modern tools and parts.
Old VW bugs didn't have computers airco or whatever, new designs all have it on a bit retro package.
Totally different from going back to the tube era i grew up in.
Nostalgia is nice, but going back impractical.