Having multiple products on a page is not really rocket science. See here for an example:
https://www.topsnoep.nl/relatiegeschenken/2863-notenmand-zelf-samengesteld.html
But there are many different scenarios where this would be welcome. Some are enhanced category pages - where people can enter quantities or select attributes. Others are enhanced product pages - where you can immediately order associated products. Yet others aim to be an alternative to the combination system, where some options are offered as separate products rather than attributes.
There is also the question of presentation. In some cases you want the cluster to appear in the cart as one product that you can delete, change quantity or change composition. In other cases you prefer to see each product separate in the cart. In some cases you want one buy button for the cluster. In other cases one button for each product.
Also related is the option to have "free" buy buttons that you can place on cms pages and pages that are not part of the webshop.
It is this complexity that makes it hard to formulate a solution. And given the needed reconstruction it is best to make one big step instead of many small ones.
You can set weights for combinations - but not lengths/widths.