Broken gear get's sent back to the manufacturer for a replacement if it's unrepairable and during the downtime the loss of hash rate would be shared among all shareholders until it is repaired or replaced by the manufacturer. "Obsolete" gear can be sold on ebay usually for more then market price /gh I believe because people on ebay are either dumb or ok with the paying a bit more because they can buy it easily with fiat. The proceded for the sale gets added to the RIF meaning less shares would need to be sold for the next gen gear and that sale benefits all current share holders.
I don't see any better sides compared to option #1 + reinvestment. It has absolutely same benefits, as you mentioned. But if you buy shares of ants hardware and in 4 years they broke down and Bitmine got shut down/bought by another company/etc, then you will pay for your buying. Not somebody else, who has no idea, why he should pay for your buying.
Having a group buy that reinvests a portion of earnings, but doesn't take on any new buyers after the round ends is impossible - no hardware generates enough revenue on its own to purchase additional hardware while still making any significant payouts to the shareholders.