It will never be valuable but Mixte frames have their fans so may sell for more than the normal gent's or lady's version of the same bike. Mixte frames are quite stylist and different from the norm and definitely worth spending time on imo.
Should be a nice, relaxing ride if you sort the gearing. It's looks to have a 46 or 48 tooth front chainwheel and probably 14-24 back block, giving a silly bottom gear ratio for anywhere that isn't flat. It would be much nicer to ride with a 40 tooth chainwheel. Don't worry about the "suicide" brake levers. If the brakes are adjusted properly with good pads, they work to an acceptable standard and are a handy feature imo.