I don't see how that solves everything at all. It simply moves the problem to someone else.
Imagine a hypothetical 2 card set.
1 - Ace Primo
2 - Duece Runnerup
20 years after release, someone notices that there are some cards printed with an * on the back and some without an *.
In today's TCDB we would have
1[a] Ace Primo - VAR: No *
1[b] Ace Primo - VAR: *
2[a] Duece Runnerup - VAR: No *
2[b] Duece Runnerup - VAR: *
Now let's pretend we have a collector that has 1[a] & 2[b]. He doesn't give a rip about the fact that the trading card company added an * to the card to represent that it came off a machine that had undergone routine maintenance after 9 months. He just wants a complete set.
- In today's TCDB he is credited with having completed the set and he has 2 of 4 cards in the master set.
- In scenario you are proposing, he has 50% of the "* set" and 50% of the "No * set". He's not happy since there is no way for him to close out this set without lying to the system about what cards he has.
And this is the simple scenario where there is an * and a non-* for each card. What about the scenario where not every card has the same variants? How do those get reflected?
Imagine a different hypothetical 2 card set.
The set is released to retail and we find the following on TCDB:
1 - Albert Typo (TCDB cid: 001)
2 - Brian Kosher (TCDB cid: 002)
The factory set is released and we discover that the manufacturer has made a correction to card #1. Card #2 in the factory set is identical.
Does a factory set parallel get created with both cards?
1 - Albert Typo NOTE: Factory set COR (TCDB cid: 003)
2 - Brian Kosher (TCDB cid: 004)
If I buy a sealed factory set obviously I know that I have the factory set version of card #2. But what if I find the card in a 5000 count box at my LCS? Which one is it? If I buy two factory sets and list one of my #2 for trade, it does not get seen as a match for someone looking for the retail #2 because they are different cid's*.
So if that scenario doesn't work, does the factory set get added with only the card that has a deviation?
1 - Albert Typo NOTE: Factory set COR (TCDB cid: 003)
I buy a factory set...do I enter in that I have retail card #2 (50% of that set complete) and factory card #1 (100% of that set complete)? Surely that's not the answer.
So I think what TCDB has done is a nice compromise.
1[a] - Albert Typo (TCDB cid: 001)
1[b] - Albert Typo NOTE: COR (TCDB cid: 003)
2 - Brian Kosher (TCDB cid: 002)
If I buy a factory set, I can mark accurately what I have. If I find a card that I don't know the origin of I can mark accurately what I have. If I pack collected the set and completed it I can mark accurately what I have and get credit for completing the set. If I buy a factory set I can mark accurately what I have and get credit for completing the set.
* I'm not ignoring what BIlly mentions by having the same cid report to two sets...I just do not know if that is possible. I believe what Billy refers to are entire insert sets that report to two sets like the 2017 Topps buybacks inserts that are linked in both 2017 Topps and 2017 Topps Update...except I notice that Topps Update actually links
https://www.tradingcarddb.com/Checklist.cfm/sid/169753/2017-Topps-Update---Rediscover-Topps-Stamped-Buybacks-Silver
that when clicked redirects to
https://www.tradingcarddb.com/Checklist.cfm/sid/153688/2017-Topps---Rediscover-Topps-Stamped-Buybacks-Silver.
(notice the different sid's [set id's])
Can cards be created with different cids, redirect to each other, and show up in want list/trade list matching reports?
EDIT: Sorry, should have quoted https://www.tradingcarddb.com/Forum.cfm/Page/I/ID/0/?MODE=REPLY&ThreadID=18295&Quote=110474#Top