Except that'd be an uphill battle from the get go. What made the Tiny Terror what it was is the simplicity. As soon as you start changing specs like that, it is no longer near the same amp. To have an FX loop that doesn't drastically alter the tone is a challenge - it requires a lot of planning for the buffer, deciding if a parallel or serial loop would be the most optimal, etc. That'd go against the premise of the TT - a simple amp to get a compressed respose and distorted sound from the power section at low volumes. Replacing the EL84s with any of the larger, higher max-wattage tubes will also increase the headroom - which may not be a good idea since the amp's only gain stage is V1 (the circuit utilizes the first half of the 12AX7 before its minimal EQ, then goes into its only other gain stage after the EQ). V2 is the phase inverter, so there's not a whole lot of preamp gain on tap. The minimal EQ is also still "needed", as it cuts extreme lows that the stock output transformer wouldn't be able to handle. The OT and PT are usually the most expensive parts on the amp, and you can't really cut costs too much on the PT (because your amp obviously needs a good power source to work) so cost cutting usually happens on the OT calling for smaller, less robust units. When you change to higher power tubes as well, you need to change both the power and output transformers to correspond to the completely new power section (first, delivering the different voltages required for different tubes, then being able to output the different RMS wattage). They'd probably need to add another gain stage in the preamp, revoice the "minimal" EQ, complicate the circuit even further with a well-designed FX loop, re-design the power section, change out the transformers. At - this point - it isn't even a Tiny Terror and the production cost is way higher (more thought required to design, more parts, more labor to manufacture, more expensive parts to accommodate the new design), but it'd be an awesome amp - because you described the already existing
Orange TH100.