This would be an amazing add on for all us dual citizen USA / UK (or other nationalities) where the complexity of planning due to accounts in different nations/currencies and varying exchange rates makes forecasting out incredibly difficult to model.
This would be great for expatriates working in a particular country but who might retire back in their home country with assets and investments in both nations. Tracking such investments would be much easier.
This feature would enable consolidation and better action for fluctuations, and hopefully will lead to more features for mixed-country planning. (I have a feeling many people in the FIRE communities would make great use of such features). Thank you for taking on the challenge!