Create a new master for that.
Edited to fix my own stupid mistake.
You might be able to acomplish this with a paragaph rule. Create a rule above wide enough to create the white space you need. Set the color to none and check the keep in frame box. This will push you text as far down the page as you need.
Create a new style for that.
Am I missing something here, Bob? I thought that Space Above a paragraph wouldn't cause the text to move down if it was the first line in a frame - that the position of the first line in a given text frame was controlled by the text frame properties, not the paragraph style.
Aack. I meant to type "create a new master for that."
Oh, yeah, that would be the way to do it.
(Although I think that SRigel's suggestion is a pretty clever bit of duct tape.)
Yes, a master...
(Although the text may change (reflow) and would be needed manually apply again master pages in the gaps...)
Sounds clever the «invisible» paragraph rule. I thought something parallel, as insert before the chapter text that begins the page a simple character (color=none) styled with the amount of blanc space required after. But this idea involved inserting one element, one style, one operation, etc. The rule before may be styled in one step and is perfect.
Anyway, it seems this case should go to InDesign Feature Requests.