I suppose something like that would be sufficient:
val newdefs = tpe
.declarations
.collect {
case m: MethodSymbol if !m.isConstructor && m.typeParams.length > 0 =>
val typeParams = m.typeParams.map(TypeDef(_))
val paramss = m.paramss.map(_.map(ValDef(_)))
val returns = TypeTree(m.returnType)
q"def ${m.name}[..${typeParams}](...${paramss}): ${returns} = ???"
}.toList