Controlling Both Show's Plotting Order and Options Generally

Question

Similar to Changing the plotting order in Show, I'd like to have control over plotting order with more advanced graphics, like a Legended ListPlot with FrameLabels. Specifics aside, I've adapted the solution from the previous question for my particular case:

Show[b, a, AbsoluteOptions[a]]

which works perfectly for me, up to the text used to label the plot and axes, which prints FrameBox["Label", TraditionalForm ] as if wrapped in one too many FrameBoxes. Placing labeling within the Show also doesn't work.

My Best Answer So Far

It seems to me the most side-effect free way of Showing things is to do the following:

1. Define desired settings in first plot (a)
2. Define other plots (b..)
3. Try Show[..b, a, AbsoluteOptions[a]]
4. For side-effected options, duplicate them before AbsoluteOptions. As placing options in Show do not perform the same lower-level routines (i.e. defining lower-level options) that functions like Plot and ListPlot do, this trick allows you to set a specific option you want (like the FrameLabel text), using AbsoluteOptions as the shim to add in all the lower-level details (like plot boundaries, text positions, spacing, etc.).

This worked in my case, but still leaves me with some open questions:

1. Where is Options better than AbsoluteOptions and vice versa?
2. What happens if your desired option is different enough from what's specified in a (using nomenclature from above) that some of the lower-level options are incorrect? E.g. say I specified a FrameLabel that was super long in Show, but not when defining a. (this is a case I could easily test, I will do so and revise this, but I also bet that this is generally a case for potential for side-effects)

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Example

Here is a faithful but reasonably minimal working example.

Answer 1

Unless I'm missing something, the following seems to work:

GraphicsOptions[Legended[expr_, ___], rest___] := 
  GraphicsOptions[expr, rest]
GraphicsOptions[g_Graphics, rest___] := Options[g, rest]

Show[b, a$with$explicit$labels, GraphicsOptions[a$with$explicit$labels]]

This relies on the helper function GraphicsOptions to extract the "non-absolute" options from the potentially wrapped Graphics expression, which are then passed to Show.