The concepts of "dynamic scoring" have been broached several times in recent years. Congressional Budget Office does include some dynamic scoring in their analysis of proposed legislation.
Dynamic scoring is an imperfect science and yet, better than static scoring. At least with assumptions based on changes, you can develop a picture of projected future outcome based on changes.
Problem is, those changes are are rarely accurate and are subject to many other factors than cannot be accounted.
I have worked the federal process under various forms of dynamic and static budgeting over the years. By far the worst was static budget (Zero-Based Budgets) of the Carter years. Talk about some off-target budgets!!!
The solution to positive economic activity is spend less than you take in. Raising taxes is not an option. Spending where the the acceleration value of a dollar cannot be realized is a waste.
The name of the game is finding a balance between "guns and butter" - defense and welfare for a GDP.
Right now, and for the last 20+ years, the scales have been tipped to the "butter" (social welfare) side of GDP. That rate is unsustainable as the Obamma deficit is showing.
Then, the current administration, like the Carter administration, are basing estimates off static scoring, unless they can show a positive economic outlook; then they shift to dynamic scoring.