The Bannerman article is pretty comprehensive but raises issue about control of the scheme as well as the allocated levies. In this case, as well as paying more, the townhouse owners have greater voting power and the Tribunal might not want to upset the balance.
One option might (an I stress might) be to get 75 per cent of owners to agree to extinguish the existing scheme and create two new schemes under a Community Title arrangement. I don’t know how feasible that is and it strikes me that it’s going to be hard to get the apartment owners to agree to any changes as they will result in legal costs followed by increased levies on a permanent basis. You can’t get turkeys to vote for Christmas.
One option might be to pass by-laws isolating apartment-only payments from townhouse-only payments. Either way, speak to an experienced strata lawyer to explore the feasibility and costs of any options.