A bipartisan group of Maine lawmakers is proposing a dramatic overhaul of the state’s tax system that includes cutting the state’s income tax rate in half. The proposal also includes raising sales and excise taxes and eliminating exemptions. The coalition has been working for several months to craft the bill. The proposal is scheduled be officially unveiled Wednesday, but a draft outline obtained by the Portland Press Herald, highlights a series of changes that would yield an estimated $700 million in revenue. Independent Yarmouth Sen. Dick Woodbury says the bill is designed to capture a more equal proportion of sales and use taxes from nonresidents in order to give tax relief for residents. The draft also calls for lowering the corporate income tax rate and eliminating the state’s estate tax.