Is it legal to set `help-char' to nil?

[YE Qianchuan]

I prefer using C-h to delete backward, thus I mapped C-h to DEL by 
modifying key-translation-map.
Then set `help-char' to nil to avoid invoking help for a list of 
commands start by prefix. (I can't find a good enough char to replace it)
For example, press C-x C-h to invoke C-x DEL but not to print help message.

If it's not legal, are there any workaround?
If it's legal, then there are bugs in certain modules like term, because 
doing such thing breaks it.

Thank you.