Given you don't want to duct it properly your choices are the larger fan your builder suggested or another drier type. If you go ducted and aren't happy your only solution is to put a duct in.

Another thing to remember is a ducted clothes drier pulls air, uses it, then throws it outside. If you don't have a window or fresh air source it's going to be pulling large volumes of heated house air in from the house, increasing your heating bills for when you replace that air.