Like maybe add tubes too?
You could. Anyone could get wild if they wanted to.
Personally, if you're going to add tubes to a circuit, you might as well build an entire amp or rackable pre-amp, which both are out of scope for this DIY group I believe.
PedalPCB builds a lot of clone circuits, but in much better quality and layouts and PCBs. There has not been a lot or any I think amp circuits/PCBs offered, but all revolve around guitar tone and why I thought this exercise would be in-line with the direction and in providing a decently powered solid state amplifier to mate with one's pedals!
Moving beyond a direct clone thou, Robert could offer a BETTER unit than what is provided in the MINI series! That is, you really get a usable (I would have to view YouTube), but like 20W, maybe 30W with the micro in the MINI amps, which just keeps up in a live band setting. To go beyond that, he could design and offer a PCB with a different micro (would have to look up which one) that actually produced 50W or more RMS and would be better than the MINI series and definitely keep up and beyond a band setting!!
Likewise, there is a passive FX Loop in these amps, which can suck tone (didn't seem to much in the MINIs), but a better one could be added, and even make switchable which would absolutely be appreciated to turn on and off say your delay!
The only difference between the higher wattage Class-D micro and the ones in the MINIs is the power supply you need, but that doesn't have to be designed as one can pick up a switchable power supply on Amazon and just need a bump (need to be calculated) say 24V @ 5A to 24V @7A for a nominal price!!
Up to Robert, but to this point, he really hasn't responded in regard to this topic!