Wow. OK.
West Ham moved to a converted athletic stadium. It is far from ideal, but it cost them peanuts and they get plenty of income from the extra capacity. We would have a purpose built stadium in this imaginary future.
A larger stadium would be a first step in growing the club. In fact, it is the only way to build the club since there is a restriction on what you can spend. We will never be Liverpool or Man U, but we could be in the next level. Players are attracted to image and big crowds. We could also pay bigger wages which is crucial and we are in London which has always been attractive.
Staying at Selhurst risks standing still or going backwards, but that is what is happening like it or not.
Improving the ground is essential if we are to stay in the Premier League. It will keep us ahead of the Championship.
I need no convincing of the benefits of a bigger and better stadium. Principally, they make a higher level of expenditure sustainable. On that basis, personally I'd be content to sell a player or two to fund the new main stand if needs be. I'd also love to see further expansion and redevelopment at Selhurst, and have posted in detail about what is involved in that.
My concerns are about the (hypothetical) prospects of leaving selhurst for a new stadium. Whilst that would bring the benefits you list, of course, it would also come at a cost. There is the cost of building it (Spurs and Arsenal fell behind in the spending race after building new grounds, the latter for a very long time).
More importantly in my view, there is also the cost emotionally of leaving home. It might not matter to some, but I place a value on walking my son to the same ground, down the same streets my father walked me down 40 years earlier. That value seems only to increase over time.
For me, it's not a question of whether a new stadium would bring benefits, it's whether those benefits would outweigh the costs. If the increase in revenue made us regular participants in the Europa League, for instance, then perhaps the benefits would outweigh the costs. I don't think that is what would happen, though.
That's why West Ham are such a pertinent warning. Their grumpiness is not just down to inappropriate stadium design (although it is awful). It's also because a lot of them felt very emotional about Upton Park, but didn't object or protest against moving because they were told it would take the club to the mythical 'next level'. It hasn't, and won't, because the economics don't stack up that way.
Even with 60,000 punters through the door every other week they still can't compete with the big boys. They still lose their best players to bigger clubs. Moyes got them in the top ten and won this daft conference thing, but not by outspending the rest. The good things they've done could have been done at Upton Park, and overall they seem no better off for the move. They are grumpy all the time because they've sacrificed their emotional roots for very little reward. Even arsenal fans will sometimes say something similar about their purpose built cash cow of a stadium.
So for me it's a big yes to redeveloping Selhurst, and a no thank you to ever leaving.
Not that it's even on the cards at all!