(pls ignore the death at the end)
My opinion after all of that ranting: Either just allow one handed ladder climbing or allow it with a stat/skill check.
Hanging off a ladder and shooting someone with a pistol is a pretty good way of getting the drop on someone. Them shooting back at you is going to really ruin your day though. Because you're not going to be dodging, and taking a bullet will almost definitely make you let go.
Yes, get a cyberarm, but if you can't afford one you should still be able to get into your pad. Climbing a ladder one handed is something anyone could do no problem. I do it all the time at work.