Voltage should be a minor issue. From what I have seen it's just an adjustment to the shunts (used to measure usage) and maybe the relays. The amperage is what really matters and that wouldn't really change. I would do the internal changes, add a manual switch on the unit to change from 110 to 220 and leave the outlets alone. Maybe supply or recommend converters (that have been tested) for EU. This would open the market more and provide a very good cost to return ratio for the overall change.
That's just what I would do though, maybe they dont have a market for it in EU (as mentioned) or maybe it wont pass testing... :shrug: