A/B & Dual FX loop switcher questions

[snk]

Hello,
I am considering building a dual FX loop & A/B switcher.
Here are my needs :
- For the FX loops : being able to route the input to either one, the other, or both loops at the same time. The FX loops run in serial, not in parallel.
- For the Output : It's either A or B.

In my head, it seems a very basic setup, involving a couple switches and that's all (I didn't even plan to use resistors).

But I am wondering :
- since it is a passive device, is there anything to consider (like possible ground or impedance issues) ?
- Would it be safer to use a buffer somewhere (i'm trying to keep things simple, but I don't want to compromise on sound quality, this circuit should help me improve things, not make it sound worse:)?
- When both FX loops will be enabled, will it make the sound quieter ?
- Should I use 3PDT instead of 2PDT, so I could put inactive FX loops to ground ?
- I know it's a diagram, and not a full-featured circuit, so I didn't draw the ground line (What I am planning to do is wiring all the grounds together). With such a configuration, is there any risk of ground loops (and, if so, how to avoid it? Should I add a « ground lift » switch somewhere ?)

[snk]

... I think I'm going to use a Klon buffer at the input, and an AMZ buffer splitter at the A/B output.