I've been into tube design and repairs for decades. The scope is not a vital tool to my own opinion, but a shorting big wire made with two clip-on pliers (one red and one black for polarity plugging), a 5 Watts resistor and a LED is a real vital tool.
You know that tension may remain in the capacitors if not properly grounded when shut down, that's why shorting them before doing anything is really vital. And for those not knowing this, there's a negative tension in most tube amps (won't go into details) that you have to discharge from the capacitor(s) by putting the shorting wire (with a LED and resistor) the other way.
Another vital device, but for the amp this time, is a loading resistor. 😉
That said, I owned the first reiusse made in the 90's bought new at the time (a hard to swallow pill) and it was a terrific combo.
I would go for the B15NF version with, as you wrote, the two biasing possibilities and also a solid state rectifier possibility.
It's a very nice project !