Over time there has been much work on understanding the USB system and the charging logic of the N900. The main fruit of this work has been enabing a very usable USB host mode for users.
With so many broken USB ports which require repair of four different pads and the risk of damaging SM components during the repair I suggest a alternate strategy.
It seems possible to create a config change, script, or app to switch from managed smart charging requiring the USB data pins to one where the user chooses max amperage and can apply 5v to the system and initiate charging where the hardware logic and software can detect charge state and end charging when full.
I understand such a software change would only affect booted phones but it would allow use of an auxilary power input including the Palm Pre Touchstone inductive charger rather than using an external charging board and soldering directly to the phones battery contacts. here is a link to Touchstone and Powermat working now http://talk.maemo.org/showthread.php?t=56950 http://talk.maemo.org/showthread.php?t=72753