Wantobe;

I'm making the assumption that you're building, since you're posting on Homebuilders and you state that you're planning your panel.

The simple answer, if you are homebuilding, is that anything goes. Not the answer you're wanting, I know....

IMOH, ideally, you'd have a single breaker for every device. That way, if one of the "paired" devices fail, you still have use of the other device(s). However, homebuilding is a compromise. While you'd have better assurance that you'd still have use of the remaining devices, at what cost? As in, not just the weight, but the panel real estate, the wiring complexity, the opportunity for gremlins with the added complexity, greater cost, etc. K.I.S.S has a certain degree of merit here.

Next, aside from the obvious note you made about making sure that the current loads are acceptable for each breaker, give some thought on the pairing. I can see why they might pair a fuel pump with lights. For the most part, you'll want the pump during takeoff, when you TYPICALLY won't be using the lights. Pairing items where their use is one-or-the-other helps reduce risk. Of course, if the fuel pump blew the breaker, and it's night, and the lights now don't work as a result, well, you see the gotcha....

I've built and am flying a day/VFR Sonex. I have landing/strobe/position lights, even though I don't intend to fly at night; I view it as nice to have if I land right at dusk, have to refuel, and then taxi back to a dark hangar. Daytime use of strobes also makes sense. I have all 3 lights on one breaker. I also have both my comm and xpndr on one breaker. I carry a handheld as backup, and, well, if I lose the xpnder, I'm typically low enough to not be of concern to DFW airline traffic. My alternator is on a circuit by itself (I have a crowbar over voltage system), and I have a master. That's it. I have a few fuses for things that don't matter.

Lastly, remember that the purpose of a breaker/fuse is not to protect the device, but to protect the wiring. Gotta keep the smoke inside the insulation.