As the mega is the most powerful variant of the arduino, it seems odd that there is no pro version; especially to replace the headers with more robust locking ones...
There are a number of arduino variants with the ATmega1280, maybe one of them suits your need:
http://www.duinoaday.co.uk/hardware.html
Mowcius
Seeduino Mega is closest - guess I'll wait for them to update it to new chip. Would still be good to have an 'official' version though.