The scheme will link the existing Stockwood Park Museum with the Mossman Collection of horse-drawn carriages through a 'new gateway building'.
This timber-framed centre will sit close to a listed garden wall - part of the original Stockwood House built in 1740 - and will house visitor facilities and extended gallery spaces.
The development will also boast a sedum roof, wood pellet-fuelled boiler and natural ventilation.
Describing the proposals, a spokesman for the Manchester-based practice said: 'This gives the whole museum a new order and creates a more cohesive site.
'Vistas through the new and old buildings are afforded along wooded walkways, with a central orientation space located to allow visitors to gain the best views and understand how the museum buildings relate to one another and to the adjacent gardens and park.'
The designs, which have been worked up with landscape architect TEP, will be considered for Heritage Lottery Funding later this summer.