Plan a WooCommerce product variation matrix for a complex SKU set

Plan the product variation structure for a WooCommerce t-shirt line:

PRODUCT LINE: [Everyday Crew Tee]
ATTRIBUTES: [5 colors: black, white, heather grey, navy, olive] x [6 sizes: XS-XXL] x
[2 fits: standard, relaxed], a possible 60 variations
IMAGES AVAILABLE: [one photo set per color, not per size or fit, since the garment
looks the same across sizes]
KNOWN FUTURE CHANGE: [a 6th color, "rust," is planned to launch in about 2 months]

Plan the structure covering:

1. Whether to build this as one parent product with 3 attributes (60 variations) or
   split it into two parent products by fit (standard tee and relaxed tee, each with 30
   variations), and the trade-off: one big product is simpler to manage in one place but
   gets harder to browse for the customer and slower to load in the admin, while
   splitting by fit gives a cleaner customer-facing choice ("shop standard fit" vs "shop
   relaxed fit") at the cost of maintaining two separate listings. Recommend the split
   given that fit, not color or size, is the decision a shopper usually makes first.
2. A SKU naming convention that encodes fit, color, and size predictably (for example
   TEE-STD-BLK-M), so a warehouse picker or a reorder report can read the SKU without
   opening the product page, and so a spreadsheet reorder sheet sorts sensibly by SKU.
3. Image assignment: set the featured image per color at the attribute level so a
   shopper selecting "navy" sees a navy photo regardless of which size or fit they pick
   next, rather than needing a photo per every one of the 60 combinations.
4. The edge case of adding "rust" in 2 months: adding a new attribute value creates new
   variation IDs, it doesn't retroactively touch existing variations, so past orders,
   reports, and stock records for the existing 5 colors are unaffected. The one thing to
   plan for is stock and price defaults on the new variations before they go live, since
   newly generated variations can default to zero stock or an unset price if the merchant
   forgets to configure them before publishing, which would let a customer order a
   rust tee that quietly can't be fulfilled.

Replace the bracketed attributes, image plan, and future addition with your own product
line's actual setup.