I was wondering the same thing for the same reasons. I just started to build my Eclips3d and chose to go 24V on everything. Namely the E3D V6 and fans since the heated bed from the BOM is already dual voltage. There is a comment somewhere on the interwebs saying that there is a polyfuse on the Azteeg that can't handle 24V so I'll have to check that out. I vaguely recall it being related to the heated bed, so I may just use an SSR for the hot bed to call it safe. I hope to let this forum know my outcomes.
Well I went 12V just because it was more basic and that's what I used on my old 3uP, plus most accessories run off of 12v (like the e3d fan and the led strip). 24V systems do heat up a whole lot faster and people are more than welcome to build up their Eclips3D around a 24V system, I just chose to stick with 12V so that is what the build is based around!
I went with 24v on my build and it's been good to me. My steppers run almost cool to the touch, cooler than skin temperature. I think about 80F. My heated bed and hot end can both heat simultaneously to 65 and 188 in about 3.5 minutes. Seems good to me.
Aside from your correct list of three items, I added a used eBay bought Crydom D1D20 solid state relay to switch the heated bed with PWM since I couldn't get Pancuit to verify the board could handle switching the bed directly at 24v. I added a configuration line to the config file to limit the PWM frequency to less than 20 per second as suggested by the Smoothieware example docs, but the SSR specs say it can handle something like 2000. So far the SSR has never gotten over a couple degrees over ambient temperature. I screwed it to my power supply case to act as a heat sink just in case. I also put a 10 amp automotive fuse in line as another precaution. With my cheap clamp meter I never saw it draw more than one amp, but it could have spiked higher faster than my meter reads. Also, I lowered the 24v power supply voltage to about 20 volts to start out conservative.
As for your other devices...like I said, the steppers work great with the added voltage. I lowered their supplied current by a tad less than half and it's working well. No skipped steps. Wires should be able to be slightly thinner gauge since they're taking less current, but I'd just leave them as the BOM items come with. The size difference is negligible. Thermistors and end stops all run off the Azteeg which provides those devices with regulated voltage regardless of which voltage the Azteeg is given (within its limits). The end stops can be powered by either 3.3 or 5v, selectable via jumper on the Azteeg.
Moved to the mods and upgrades section. Thank for your trials with 24v, I'm sure many people will benefit from this if they were looking at doing a similar mod! I will definitely be switching to 24V systems for any future printers I may build!