Excusing turbocharger/MGU-H reliability for a second, the increased pressure ratio required by the ICE to compensate for altitude will show an increase in compressor outlet temperatures. This can create problems for the PU's that seem to be the most knockI limited (appears to be Renault at present).
I'm curious to see how teams will compensate for this. More open bodywork with larger intercoolers will be the traditional and most obvious route. Especially considering the lower density air may create cooling problems outside of just inlet air temperature.
For those teams running an air-water intercooler setup they may use a larger intercooler coolant tank. This is not really ideal and comes with a weight penalty and the penalty that once all the water has heated up you are in the same position as everybody else. However it can be used to give a few laps extra at a higher power setting (assuming the intercooler isn't enlarged)