Sorry but I think the opposite.
If you are a weak site with few back links and a low domain authority then you need to concentrate as much juice through as fewer pages as possible whilst retaining a strong fairly flat hierarchy. You don't have the option of doing nothing as you are cannibalizing your site in search.
I deduce from what you are saying that you have this problem.
Site/size
Site/Collection-1/Size
Site/Collection-2/Sub-collection-1/Size
So the size filter can be applied to any part of the site at collection level. You may also have
Site/Brand/Size
Site/Brand/Collection/Size
Site/Brand/Collection/Sun-Collection-1/Size
Then you will have maybe
Site/Sale/Size
Site/Sale/Collection-1/Size
Site/Sale/Colelction-1/Sub-collection-1/Size
On top of this problem you will have
Site/Brand/Product-1/Size-29
Site/Brand/Product-1/Size-30
Etc
I hope I am right!
Solution for Brands and Categories
it is better to have size as a tag and noindex/nofollow the tag group so that none of these extra pages get indexed in Google. This will make an enormous difference to your website slashing the number of pages with skinny content and visits right down.
You simply can not have these pages:
Site/Brand/Size
Competing with the main brand page ie
Site/Brand/
I don't know how many sizes you have but say there are 20, then it's like having 20 duplicates of the brand page, the category page, the category/sub category page.
Solution For Products.
Have one product page:
Site/Brand/Product-1
The sizes can then drop down on the page without changing the URL - the canonical on any size is thus
Site/Brand/Product-1
Some sites will append the tag for size thus:
Site/Brand/Product-1#size30
With the size as an attribute - everything after the # is not indexable as Google does not go beyond a #
It would also be prudent to do this for colour as well otherwise you will get mass duplication at colour level. That should also be treated as a tag or attribute that does not append to every version of a page.
I really do hope I have understood this correctly.
I repeat, You don't have the option of doing nothing as you are cannibalizing your site for search.
eCommerce site structure is core to my business.
Kind Regards
Nigel