I don't know if the by-pass valve piping in the unit mentioned by the OP could be modified for convenience, but many things like this can be improved. I would think in the interest of longer pipe runs; less antifreeze and simplicity they would have to be near the HWH???
My XLR 29HFS had several poorly planned or poorly executed examples including the fresh tank drain. It wasn't as difficult to get to as some mentioned here, but the factory with a piece of 1/2" PEX and a couple of fittings dropped it straight down from the drain hole; actually unnecessarily close to the ground. I replaced the pipe; routing it to the outside, which is easily reached.
I would say most if not all the poorly placed drains could be easily extended to one side or the other without running them uphill.
Getting to fix and upgrade is the fun part of RVing... don't you think?
I will say that many small things on my XLR were done right and are convenient, of course, only the things that are not, draws one's scrutiny.
If the supervisors at the factory were doing their jobs, these small problems that we bring to this forum, would all but be eliminated. Because, I doubt that the fine detail of the build are laid out exactly for the assembler.
XLR Hyperlite 29HFS
Ram 2500 6.7L CTD
A Modder's work is never done!