Hmm Chris, I've seen this done a couple of different ways in a few different companies. Not sure I would include it in a double dimensioning way. It's not really a dimension.
It will all depend on the company standard. What is typically done at your job. Or ask the checker if you're fortunate enough to have one.
No harm no foul. But consistency would be key.
I am not sure. I sometimes do this same thing. I don't think that it is as long as it is clearly defined.
I sometimes make stepped exploded drawings. In which, on the first sheet will be the entire assembly (assembled) with a BOM. Then, I will break down the assembly process into steps and make each step a sheet.
So, simple example:
1) Assembly has 1x base plate, 2x mounting brackets, 2 covers, 16x 1/4-20 x 3/4" long SHCS, 4x dowel pins
2) Sheet 1: Shows assembled assembly and BOM which shows the quantities listed above
3) Sheet 2: Shows Base Plate and 4 dowels, complete with 1 assembled view and 1 exploded view. Assembled view shows dimensions to show distance dowels need to "stick out". Balloons on exploded view point to Base Plate and then to 1 dowel with 4x as quantity.
4) Sheet 3: Shows Assembled Base Plate with dowels, and now addition of Mounting Brackets with SHCS. Exploded view has balloons that point to 1 mounting bracket with quantity 2 and another points to SHCS with quantity 8
5) Sheet 4: Shows Assembled Base Plate with dowels& Mounting Brackets, and now addition of Covers with SHCS. Exploded view has balloons that point to 1 cover with quantity 2 and another points to SHCS with quantity 8.
Of course....this is a very simple example. And nowadays, I tend to break this up into separate sub assemblies (Like a sub assembly that just has the base plate and the dowels.)
But I still do multi sheet drawings like this, just to show assembly order and to lessen the chaos of the sheets.