A bleed air system which works by providing airflow and not only pressure would be nice, too.
The Q400 can produce over 100 psi of bleed pressure creating lots of noise from the gaspers but ventilation is still poor.
And speaking about air conditioning the dependent bleed ducts which can't be more than like 10 kelvin apart from each other are just silly.
A full load of passengers require cooling even on a cooler day but the guys upfront will be freezing as they can't select the duct temp high enough without baking their passengers...