1st option. There are many hidden traps, when you go with securities of total operation. Most people only interested in GHs/$ rate. And if you are going to compensate hardware failures/obsolete from total operation, then you will need either: 1) sell new shares at high GHs/$ rate (that nobody will buy) or 2) sell shares that include both new and obsolete hardware. This will again decrease value of your sells due to (for example) increased power consumption. And nobody will be interested in buying obsolete hardware, when enough good offers will be around. There are plenty of these kind of companies and most of them are going to dead end.
In other words, problem of option 2 and 3 is: you can't sell shares, that have infinite lifetime. (only exception: if you are selling overprices shares and somebody still buying them. Then they will life as long as you could find investors).
I'm not sure why you would have to sell shares at higher rates. The rate would depend on how much that hardware costs.
Let's say R1 was a batch 2 Neptune and sold 300 shares at $33/share. 3000 Ghs for 10,000 so $3.33 per ghs (10Ghs/share). The coop runs it for 2 months paying out dividends of 50% to the shareholders. Now the coop has let's say 5k worth of btc in a reinvestment fund.
R2: The KNC X comes out around that time and it's 10Ths for $10,000 so this new hardware costs $1 per ghs. so the coop takes their 5k and 150 more shares are sold at $33 each.
Now the pool is up to 13Ths with 450 shares and now everyone who owns a share is running at about 29Ghs.
R3: A couple months later the neptune is obsolete so we sell it on ebay for $2000 and KnC puts out the X2 which is now 50Ths for $10k. So there's 5k in the reinvestment fund plus 2k from the sale so now we need to raise 3k. 100 shares at $30 ought to do the trick now we have 60Ths divided by 550 shares so 110Ghs per shares.
I see no reason why this model would die as long as BTC is alive and well.
Obviously I'm throwing out arbitrary numbers but I think it makes the point I'm trying to get across.
FYI: By R3, R1 has made their roi collecting 50% and they are now just sitting back collecting dividends.
In your example, at R3 you can't sell 3000GH for 2000$ (0.67$ per GH), when 50k for 10k$ (0.2$ per GH) comes out.
And even then you are going to sell R3 shares at 0.27$/GH rate, that normal ppl won't buy.
Yea, you can play with arbitraty numbers.. but in the end, you will either sell overpriced shares or steal from old shareholders (option #3 + some tricks with numbers).
It happens because of: you are selling infinite lifetime shares for hardware, that has limited lifetime.
Edit: you can make reinvestment
in Round. And it will work good. But, when you merge and add new rounds, somebody will always pay more. And it will bring fundamental problems for operation earlier or later.