The structure of Gov. Maura Healey's transfer tax plan could box out lower-income communities from using the local-option policy as a tool to generate money for affordable housing in their cities and towns, according to a lawmaker who hopes her alternative approach will land in the Senate's version of a major housing bill."I've heard from communities that are excited about this as an option, but are concerned because it wouldn't work for them," said Sen. Jo Comerford of Northampton.Comerford and Rep. Mike Connolly of Cambridge filed a bill (H 2747 / S 1771) seeking to broaden the scope of which real estate transactions could be subject to a potential tax on property transfers.Under the governor's plan, the local legislative body of any municipality could adopt a fee on housing transactions of between 0.5 percent and 2 percent of the portion of a sale above a certain amount. The threshold would be $1 million or the median single-family home sale price for the county where the community...