There are no security implications, on the contrary.

It is objectively cleaner to keep your user scripts in your home, that way they are only in _your_ PATH, whereas putting them in /usr/[local/]bin implicitly adds them to every [service] user on the machine, which I can see creating obscure undesired effets.

Not even mentioning the potential issues with packages that could override your scripts at install, unexpected shadowing of service binaries, setuid security implications, etc.