It doesn't seem like you've actually tried anything and have merely discussed what you might want do. Most of what you are concerned about are non-issues. InDesign is geared for this type of stuff. It may be beneficial to open InDesign and discover what you can or can't do with related to graphics, inline objects, and anchored objects.
What you seem to actually want are anchored objects and not inline objects.
There's a subtle difference.
Inline Objects are pasted or placed inside a text frame while the text cursor is active in the text frame. This essentially locks the object to the text frame boundaries. Inline objects are treated like a large glyph rather than an object themselves. They adhere to the text alignments, leading, etc. (Although you should be able to extend a graphic frame outside the text frame. Not sure what you are referring to there.)
Anchored Objects are pasted or placed without any text frame being active. You can then "anchor" the object to a specific piece of text in any text frame. The anchor becomes relative and will move the object when that text moves. Anchored objects pay no attention to text alignment or leading beyond ensuring they remain the same relative position to the text they have been anchored to. Anchored Objects are not restricted to any text frame. You can freely move them around on the page and extend them beyond text frames.
So they are kind of, sort of, similar.
You can convert inline objects to anchored objects by just clicking the anchor icon () and dragging to a place within the text you want to anchor the graphic. (
View > Extras > Show Anchored Object Control if you don't see it.
Using anchors graphics with text wraps should make pulling off your sketch a simple thing.