That is a pretty bike. If upright bars well allow you to enjoy it more, then go for it. Changing back to drops isn't too difficult if/when you decide to sell. That said, if I were in your shoes with the rationale presenting in the original post, I'd seriously consider a taller stem for the Paramount and converting one of your other bikes (perhaps one of the Rivendells or VO Campeur) to a flat bar instead and keep the Paramount as the classic beauty it is.