I think you're right that the estate of Longbourn would be a lot more appealing if Mr. Bennet were already dead. That would be a different situation and yes, I agree, would make it a desirable estate.
I'm mostly making my assumptions about the size of Longbourn based on one fact, which I will freely admit is pretty tenuous: there is never any admission of a ballroom. There's a book room for Mr. Bennet, a drawing room etc, but no ball room, whereas Netherfield seems to have one, or at least to have a suite of rooms that could easily be used as one (I think it's implied that Jane and Lizzie share a bedroom, too, but I don't think that was really uncommon anyway, and they obviously have a guest room for Collins, so if they do it's not through sheer necessity). It's not much but that's the reason for my assumption that Netherfield, if properly inhabited, would be the major estate in the area. It is true, however, as you point out, that Bingley's money and Jane's estate would allow them a style of life (probably even with the family to support, and you're quite right that Bingley's character is too generous to object to that) that would allow them to be leaders, if not THE leaders, in the neighborhood.
I think your setup would be interesting. It does not seem to me the most natural result of the situation, but I would be intrigued to see somebody write it! It's fun to see how differently different minds work.
I'm mostly making my assumptions about the size of Longbourn based on one fact, which I will freely admit is pretty tenuous: there is never any admission of a ballroom. There's a book room for Mr. Bennet, a drawing room etc, but no ball room, whereas Netherfield seems to have one, or at least to have a suite of rooms that could easily be used as one (I think it's implied that Jane and Lizzie share a bedroom, too, but I don't think that was really uncommon anyway, and they obviously have a guest room for Collins, so if they do it's not through sheer necessity). It's not much but that's the reason for my assumption that Netherfield, if properly inhabited, would be the major estate in the area. It is true, however, as you point out, that Bingley's money and Jane's estate would allow them a style of life (probably even with the family to support, and you're quite right that Bingley's character is too generous to object to that) that would allow them to be leaders, if not THE leaders, in the neighborhood.
I think your setup would be interesting. It does not seem to me the most natural result of the situation, but I would be intrigued to see somebody write it! It's fun to see how differently different minds work.