While you could "de-fiddle" subsets of the table contents to assign to separate clients this way, I'd say there's little actual value to this approach. This is because separating the data sets would implicitly change the compression that SAP HANA applies to the single columns, thus leading to different actual space requirements.
In the end this would lead to over-counting, since it each client has it's own range of distinct values and those likely will be overlapping.
So, what I would propose for this is to apply a form of fixed costs accounting.
One simple approach would be:
1) find the share of data volume measured in records each client takes up in the specific table.
2) take the total space requirement for the table and distribute it to the clients based on their share from step 1).
This would provide a reasonable accounting for an as-is analysis.
Obviously, this would only be so useful when planning for a system copy (maybe to another platform) since then you cannot count on the same compression factors.
my 2 cts