There are at least three additional forward linkages that could be usefully added to the model. First, we know that morbidity affects health spending, but the model does not have that relationship (change in health spending is linked instead to change in GDP per capita). Because health spending competes with other government spending (IFs does not represent private health spending separately from public), adding such a linkage would affect other spending and/or the total expenditure and revenue balance and therefore the level of taxation.
Second, we know that health affects the ability of populations to obtain education and the quality of that received. IFs includes enrolment terms to which health could be added. Third, health will affect distribution of income and economic well-being, although that relationship might be particularly difficult to represent.
Certainly there are other forward linkages of mortality and morbidity that the model might include.