I agree the benefits of the charitable status. It also provides a higher lever of trust when fund raising with members of the public I think. The key funding bucket though is actually for charities which are social enterprises. Some of the recent funding has been specifically for these types of organizations such as the last call under the Dormant Accounts Fund.
However, in order to be an official museum as awarded by the Heritage Council, the heritage artifacts must be static / cannot move under the current interpretation of the Heritage Act 1995. So, in my experience, heritage railways in Ireland cannot go down this route unless they have a separate static collection with a preservation plan and appropriate facilities for these items.
The WSVR raised this with the Heritage Council, and the Minister for Heritage in the last government, and was not the only organization to do so.