Custom modelines probably won't help.
VESA VBE is rather limited, there is a list of predefined modes that the BIOS/Video vendor configure.. using a mode not in this list isn't possible, so various tools have existed for some chipsets, but generally they're not to be relied upon.
Until a driver exists for this Intel chipset (..seems to be a rebranded
PowerVR) you're mostly out of luck.