The descriptions of the well, make it sound like it is capable of containing the coin collection. Especially with a warden with soul hire, and a pseudo nephlim spirit of intellect daughter.
I suspect it would be useless. Oh I agree the well could contain the fallen angel. But it would be pointless. The coins represent an agreement between the angels and the fallen angels. Imprisoning the coin in the well would not change that agreement. A new fallen angel might be sent out to replace the imprisoned one.
It can be argued that imprisoning the coin is a mortal decision and thus would be honored -- but I suspect there would be other consequences to balance the scale.
I personally think balance requires the angelic forces to hold back more when a coin is imprisoned then when the fallen is actively working in the world. This applies when a coin is held by the church or any other safe keeping. However, when the coin is in the world actively tempting someone, that counts as fallen activity. If this is true, then Harry having the coin for a few years without using it (despite temptation) would then have been a good thing -- allowing angelic intervention without also allowing fallen evil to occur.
The blessed cloths the Knights and Forthill cover captured coins in seem to prevent the other Denarians summoning a compatriot's coin back to them
The coins are all about choice. That is why a fallen cannot just put a coin in your hand to corrupt you. It does not work that way. I suspect that choosing to give up the coin operates the same way in reverse. It blocks the person from calling the coin. I suspect the only people who "could" call the coin are people who choose to take a coin, but have not yet given it up. Even other fallen could not summon a coin.
As for sacrificing a Denarian, I think the only thing the Table would get is the personal, innate power of the Denarian. The Coin is more like a weapon or a carried object, it probably makes no more sense to talk about sacrificing a Coin on the Table than it does to ask what would happen if you sacrificed Harry's .44 or Stallings' badge on the Table.
The Denarian is the possessing spirit. It has no blood to be spilled on the stone table. The possessed mortal does have blood, but the fallen angel power is not imbued in that blood. So quite doable, but not very useful assuming you can make it work in any case.