Lots of interesting suggestions. Some thoughts:
Delayed closing
I’m against it. It’s sort of possible already to delay closing by using a low btc fee. Conversely, if you want to close immediately, use a high fee. I think this simplicity/flexibility is good.
And as you mentioned, a bad actor could front-run dispensers anyway.
Close to creation address option
This would be a great feature! My only concern is the length of the message data. Dispensers already use 84 bytes when oracle feed is added. Would be great if this option can fit an 80 byte op_return somehow.
Allowable address option
Great suggestion! Maybe this should be a new message type tho? Unlike dispenser, which require 100% trust (and is currently being used VERY IRRESPONSIBLY), the allowable address option will require no trust.
It should be easy to build infrastructure around such a contract too. I will write a separate post about this. IMO potentially a very useful upgrade to Counterparty.
Expiration option
This is something I want and certainly would use. Again, my only concern is the message data. Maybe bundle several such upgrades to a new tx ID, and make the op_return message more efficient to fit 80 bytes?
Use/Reuse any bitcoin address as a dispenser
Does your suggestion open up for scripts/wallet not using API to put dispensers on any address? A solution on the protocol level could be to let an address send a broadcast to open it up for dispensers. I believe something similar exists, require memo, where an address broadcasts that it only accepts transfers with a memo.
Allow dispensers to sell ‘packs’ of cards
Isn’t this already possible by setting up multiple dispensers on one address? If anything, I’d actually like to allow several dispensers of the same asset on the same address. It opens up for 3 for 2 offers etc. (Would be possible if one dispenser has price 0.1 and the other 0.2).
Two more topics I’d like to discuss:
Reservation
If partial dispense is detected, reserve token for 12 blocks. If a second tx is made within the deadline, and the amounts sum up, then make the dispense.
This will remove the need to trust the seller. IMO a very high priority should be to add either this feature to dispensers or a new OTC contract.
Random dispense
Send BTC, have a 1/X chance of getting the token. The block hash is a perfect random number. This should probably be a new transaction type under a different name.