Idea 1: It would be beyond fantastic if incremental find did what Google Chrome does - highlighting all finds in the document, and showing their positions in the scroll bar "track". I'm sure Chrome's source will provide some implementation tips.
Idea 2: When incremental find is in focus, pressing the current IncrementalFind shortcut should select-all contents of the input field to allow for a new search. (Ctrl+A works, but is less convenient physically and cognitively.)
Minor bug: I have noticed in Textpad 5.4 on Win7 x64 that when exiting the incremental find with Esc, while the current selection is correct and gains focus, the actual caret is at the top-left of the view - which is a bit disconcerting.
btw - I think implementing collapsible blocks would be a ruinous idea. TextPad's syntactical agnosticism is what makes it so great in my book.