Unlike converting from DVI to say HDMI, simply making a 'female' minidisplay port does not solve the problem as you wish. it is electrically much more complicated than that, as the 'old' interfaces like HDMI have much of the signal circuitry on the display side, where as modern interfaces like DisplayPort put the drive circuitry on the output side. So, there simply are not the electrical guts inside the ACD to accept and process an HDMI signal. To do so, you'd not just have a physical adapter but something that would have to recreate the MDP signal. This is unlikely to happen for a reasonable price (i.e. the cost of a simply 'HDMI to MDP' adapter' anytime soon).
Going the other way is no problem (MDP to VGA, DVI, etc) as the legacy connectors have the large and expensive circuitry in the displays to interpret the signals.