I would rather take a different approach that consists in separating the fiscal stance (i.e. the size of the public deficit) from the instruments of that policy (the tax rates and public spending).
You would have a single γ parameter appearing in the equation determining the fiscal deficit. For a eurozone country, there’s a natural value for this parameter, given by the debt criterion of the Stability and Growth Pact. It is equal to 1/20 (in annual frequency), assuming the steady state debt is 60% of GDP (in reality, the criterion states that it’s the 3-year moving average of debt-to-GDP that should be diminished by 1/20th of its distance to the 60% target).
Then you need to decide how to implement that policy. There are many options. One is to have all instruments constants, save one which will bear all the adjustment. Another option is to have the share of all taxes constant in the total tax revenue (and probably keep spending constant).