You have two factors at play here. The first is what is says on your strata plan and in your by-laws (which is nothing, by the sound of it) and the other is the principle of accepted use. In the absence of any clearly and legally esablished division of the space the CTTT is likely to rule in favour of how the space has been divided and used in the past, especially if there has been no previous objection to its division in that way.
If the proposed division of the space is based on numbers painted on the wall that have been ignored for years, I would think it wouldn’t stand up to much scrutiny at,, say, the CTTT.
I would suggest mediation (it’s free via the Community Justice Centre) but the EC should think about employing an experienced strata lawyer or a specialist surveyor to draw up by-laws that will sort this out once and for all.