Thank you for giving more thought to this issue. Unfortunately, your rationale doesn't quite stand up to scrutiny.
The fact is, for more than 40 years the BBWAA has employed fuzzy rules in deciding who makes the ballot. Since 1968, the BBWAA screening committee employs subjective criteria in deciding which 10-year players among those retired five years ago will actually appear on the ballot. The perils of this subjective process were starkly revealed in 1978, with the flap surrounding the screeners' rejection of Milt Pappas.
Given this history, it would not be much of a reach to give the screeners the authority to put on the ballot players who made only token appearances in the five years since they last played substantially. For example, they might be allowed put players like Sandy Alomar, Jr. on the 2012 ballot, ignoring his 8 games, 22 PA at age 41 in 2007. However, I don’t advocate for this; we know how an arbitrary process such as this can lead to controversy and charges of favoritism. I think we would agree that there ought to be
objective criteria used to decide eligibility for the HOF ballot.
You asked, where do you draw the line? Employ Occam's Razor; or KISS. In other words, try to keep it simple and sensible. Follow the wording of the BBWAA Election Rules: “Player shall have ceased to be an active player in the Major Leagues at least five (5) calendar years preceding the election.” Taken literally, rather than technically, Snow was not an “active player” in 2008. Snow didn’t try to work himself into game shape in 2008; his intent was never to actually be an “active player”, but simply to be honored in a Giants uniform.
The Snow Affair is an opportunity to clarify the rules and set them aright. Rule 3.C of the Election rules should be amended to define the term “active players” to conform to Rule 10.23(c) of the Official Baseball Rules regarding consecutive-game playing streaks. So add something like this to HOF Rule 3.C: Unless a player plays at least one-half inning on defense or completes a time at bat, in the regular season or the post-season, he will not be considered to be an active player in that season for purposes of HOF eligibility.
That’s where you should logically draw the line. The rule that defines a “Game” that serves to continue a player’s career should be the same as the Official Baseball Rules that define a “Game” that serves to continue a player’s consecutive game streak. J.T. Snow’s appearance in 2008 would not continue a consecutive game streak, according to Rule 10.23(c); likewise, it should not be counted as an active continuation of his playing career.
The Hall of Fame should encourage the BBWAA to address this modification to the eligibility rules.
I hope this helps,