Thanks for reporting this important issue.
Great feedback and suggestion. I’ll see what we can do accommodate that type of translation solution in the future. In the mean time, here is an example of how you might translate custom field labels established from the Dashboard, by translating them at runtme using an s2Member action hook in WordPress.
NOTE: This is normally NOT necessary, because site owners operating in a different language, can simply enter the Field Labels in the Dashboard, in the language they prefer to use. However, in cases where you’re attempting to support multiple languages with a single instance of s2Member, this may assist you.
Please create this directory and file:
/wp-content/mu-plugins/s2-hacks.php
(NOTE: these are MUST USE plugins, see: http://codex.wordpress.org/Must_Use_Plugins)
(See also: http://www.s2member.com/kb/hacking-s2member/)