I reached out to RepRapElectro and this was their reply:
Quote
RepRap Electro
From an electronic point, it is possible, the mosfets that are used for the heat-bed and for the heat-0, fan-0 and heat-1 connectors are the same, however they are using different power rails. The heated bed uses a separate power rail which is protected by a 15A fuse while the heaters use a different power rail protected by a 5A fuse.
The fuse for the heaters can be replaced with a similar fuse with higher current rating but it will be sharing the current with the hotends and fans.
The fuse is a Nano2 fuse and Littelfuse has one rated for 15A with part number 0448005.MR (http://www.littelfuse.com/products/fuses/surface-mount-fuses/nano-2-fuses/448/448015.aspx).
The RAMPS for example uses a fuse of 11A for the heat-bed and a 5A fuse for the heaters and motors, so I think 15A should be able to handle both the additional heat-bed and the hotends, you may want to check the current requirements of your heated beds.
An alternative solution could be to replace the 15A ATO fuse for the heat-bed and wire both heat-beds to the same connector on the RAMBo, the mosfet itself should be able to handle up to 60A.
You will however have issues if the heat beds don't reach the same temperature at the same time, as you won't be able to control both separately. The connectors themselves might also not be suited for such a high current, so I'd be worried that the connectors might melt.
In either case though, know that these are not tested configurations and while they should work, there are no guarantees that they will.