Maybe do a search for Car Audio Battery Terminals.
What you have to keep in mind is if you have a 10 gauge off of the battery post for let's say the fuel injection, then there needs to be a fuse on that wire close to the battery. If you then have another 10 gauge going to let's say a cooling fan, then this wire too also needs a fuse on it. If you have headlight relays then there will be a wire off of the battery for it and it too would need a fuse on that wire.
Maybe lay out what you all might be needing to connect to the battery and then layout for some future upgrades and then run a short feed wire off of the battery to a fused distribution block.
The reason companies tell you to go directly to the battery is to limit voltage drops. If you were to tap into an existing wire somewhere on the car and it's already stressed and then add in something like the fuel injection, then the power might be reduced and the circuit overloaded. I know years ago when I was trained by the factory on Clifford Alarm systems, they too wanted one to make the main power and ground connections at the battery and I had a car he looked and and asked why I wired up to the starter solenoid on the fender (a Ford factory setup) and then where the ground wire from the battery connected to the fender and my response was I was worried about corrosion on the posts and this was as close as I could get with VERY minimal voltage drops and would not have to worry about corroded terminals affecting things. He aggreed and passed me for my installation certification.
I saw something similar used for a stereo installation, so I have searched for "audio", "multiple", "multi" etc. The best one I have found so far is the Hydra, and I might get a set of those. I was hoping for something smaller though, basically something like a standard, "parts store" terminal with three bolts. Or maybe a crimp-on terminal with a few accessory bolts.
One thing I don't like about the EFI harness is exactly what you say: The fuse should be close to the battery, but the harness has a 30 A fuse holder on the engine end of a 12 ga feed wire. If voltage drop is the only issue, I think I can rearrange the EFI harness a bit and actually get less drop. I installed a fuse block on the firewall not too long ago, fed by a 6 ga cable and protected by an 80 A fuse right behind the battery. If I hook up the EFI feed to the fuse block, I should actually get voltage drop than running the 12 ga wire all the way to the battery. This would also eliminate the unprotected 12 ga wire, so it should be a win-win.
I'm going to install a new engine/transmission, fuel pump and a few other upgrades within the next couple of weeks, so for now I'll probably improvise the battery connections somehow. Once everything is up and running, I can start rewiring everything to go through the fuse block. I think it would be unwise to dig too deep into the wiring changes before I know that everything works.