Using Canvas for Figures creates large files

Hello, I am looking for a solution / help regarding file sizes.

To describe the problem I'm facing: We have a lot of Word documents describing different tasks. The documents contain a lot of pictures, some with many inserted shapes to highlight / point to a certain things. 
Currently I use Drawing Canvas to keep the pictures and shapes in place and not to fall apart when editing. The problem is, doing it this way, the file size dramatically increases. I have compared the same document with figures in Canvas and another with pictures inserted without Canvas, the size increases drastically (e.g. form 10MB to 120MB).

Some things i've tried:
  -Not using Canvas - obvious, but the shapes and figures do tend to fall apart, leaving small shapes scattered in the document. The documents are edited by many users with different levels of Word knowledge and attention to detail, thus rendering this solution unviable.
  -Using Tables to anchor the shapes - this also proved unviable, because when deleting a picture from the table, the cells resize regardless of the shapes (which are still anchored to the table itself, but are now outside of the table overlapping a text), and when deleting the Table, the shapes remain.
  -Inserting already edited pictures - while this solves the problem with shapes, it is also unviable, because the shapes often changes. Creating a collection of stock pictures that can be re-edited to suit changes could resolve this, but there are thousands of different pictures, so that would be counterproductive.
  -Using an alternative software to Word - unviable due to internal restrictions...and the fact that almost everyone has at least some experience with Word to be able to edit a document.
  -Compression of pictures - that is the only "kind of" working solution, but another problem was discovered. When trying to compress all pictures and deselecting the option to "Apply only to this picture", strangely not all pictures get compressed. When multiple pictures are in a Canvas, only one picture gets compressed. When pictures are "Grouped" with shapes, sometimes the compression skips them entirely.

Hopefully my description of problems is understandable...
Thank you all in advance 🙂