I've actually been working on making some weighted metrics in workspace recently, it should be possible with the use of the advanced functions.
There is a function for "column sum" - that will likely be very useful for your weighted metric calculation. For example, a very basic formula, to see how individual items contribute to an entire metric, you can do something like this.


The column sum is great because it adds up all of the rows, and then you can look at an individual rows contribution to the entire sum. The only issue with this is that it doesn't deduplicate data. For example, if I were to use visits instead of page views, it would could all the visits for all the pages in the table, massively inflating the visit count. There might be a way around this by using multiple other functions/calculations, but I haven't solved for it yet.
Like Jen mentioned, if you share the formula you use in excel for your weighted calculations, we can help replicate it in the metric builder.