What is your reasoning behind the Pentode/Triode switch? Typically this is done to cut the power in about 1/2. It does change the tone a bit, maybe thats what you are after?
If you did as you were describing, you probably want to put a couple resistors in. I would have a 1.5K 1W resistor on pin 4, then a 1M resistor, in parallel with the switch lug (see crappy drawing). Then the other lug like you described.
You would be be fine to put standby here, thats what I do on our Renovo amps. Very similar to what you described. We use an On-OFF-ON NKK switch so standby breaks the connection to the Output Transformer and the Power line has to go through the 1M resistor.