Perhaps a developer who is willing to fight any NIMBYs who think that higher housing density will devalue their properties or encourage what they consider “undesirables” to move in?
If the lot is big enough, perhaps build a new house on a different part of the lot and keep the small cottage as an ADU? Although if the small cottage is where you want the main house, moving it to a different part of the lot may be more work than it is worth.