Your ideal solution is not possible with floating shapes but it is easy with Inline shapes which plays straight into Stefan's suggestion. AFAIK you can't have an anchor on a different page to the graphic.

The point of 'fixed on page' is to always position the graphic at the same place on the page - but it is always going to be the same page as the START of the paragraph it is anchored to.

If you want to use a floating graphic on the page but don't want any line text to also be there then simply anchor to an empty paragraph. You can set the floating graphic to sit in front of the text if there isn't space for the empty paragraph to sit on but you will need that paragraph and the following paragraphs to have page break before turned on if you want the floating graphic on its own page. If you have two graphics taking up all the space, put two empty paras on that page and set the anchors to the correct paragraphs to get the numbering in the right order.

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Andrew Lockton
Chrysalis Design, Melbourne Australia