It is indeed refreshing to read of effort being applied to understand the scripture and 1 Corinthians 15 in particular. I understand verse 20 through verse 28 as parenthetical to the context flow, a sidebar if you will, thus helping to provide a contextual beginning and end.
There is a widespread tendency to view the classes in verse 23 as pertaining to a resurrection sequence but they most certainly are not. The action (verb) that is applicable to verse 23 is found in the last word of verse 22. The Greek word is rooted in zOopoieO, but in this verse it is in the future tense ( zOopoiEthEsontai). KJV translates it as "shall be made alive", while the Concordant Literal Version as "shall be vivified". Either way, the classes detailed in verse 23, and maybe verse 24, pertain to future vivification, not resurrection. I believe the reason for vivification rather than resurrection is: vivification does not require a physically dead body, resurrection requires such a condition. Vivification can and does occur even while we are yet living. If you follow zOopoieO along in scripture you will discover this to be the situation, consider starting at about John 5:21.
In verse 20 Christ is risen from the dead, additionally He is identified as the "firstfruit" of them that slept, a particular class of "the dead". Christ has been resurrected. There is no future resurrection and/or vivification for the man Christ Jesus.
In verse 21 a contrast between "death by man" and "resurrection by man" lays the groundwork for the forthcoming sequence of vivifications. The head of each creation of humanity is stated, then further identified in verse 22. In verse 22 a comparison between "all" in Adam die(present tense) and "all" in Christ "shall be made alive" (future tense). The new humanity in Christ commenced at His resurrection, this is reference point for the future tense.
Verse 23 provides the sequence of vivification of the "all" in verse 22. These vivifications occur after His resurrection, thus the future tense use of (zOopoieO), in an orderly fashion, not by willy-nilly or all at once. Each is vivified in particular order/class (tagma-only here in the new testament).
Verse 23 indicates three "orders", the first two orders/classes are "aparchE" and "christos" (firstfruit and anointed). These are simply two unadorned nouns. It is best to use "anointed" rather than "Christ" (see caveat # 4 below). Christ has no possible future tense vivification – He is currently alive, as "beartheweak" has rightly observed. That there is a class/order called "anointed" may cause some challenges to usual interpretation, but the text better supports "anointed". "AparchE" and "christos" are typically jammed together in such a way that produces a untenable contortion of the text, such is not necessary. In the Greek text the definite article in "Christ the firstfruits" (KJV) is not present. That there is no indication of a time factor separating these two classes simply means that they can run concurrent within a time frame (or at least with some overlap), or that the class "christos" can be vivified at most any time, without reference to another timed event.
"Afterward" (epeita), in verse 23, does introduce an element of time, duration is uncertain but sequence is sure. After the "aparchE" and "christos" (firstfruit and anointed) vivifications comes the next vivification and it is inextricably linked to "the coming" (parousia) of Him. Of whom? Of Christos, not christos. Jesus Christ has a (parousia), "the anointed" class does not, thus Christos, not christos. This is group three.
Verse 24 is introduced with "then"(eita), a time factor. After the vivification related to His (parousia) then a final vivification occurs at "the end"(telos). This fourth group receives vivification "when" some other "end"(telos) events come to fruition as given through verse 28.
By the end of verse 28 the "all in all" will have been vivified.
A few caveats:
1) In the new testament firstfruit (aparchE) is always singular.
2) Vivification (zOopoieO) does not necessitate resurrection, nor vice versa. Examples of vivification without an accompanying resurrection: John 6:63 has "….the spirit that quickeneth…" and 2 Corinthians 3:6 "…. but the spirit giveth life." Examples of resurrection without vivification (zOopoieO): The resurrections of Lazarus in John 11 and of Tabitha in Acts 9. John 5:21 has Father raising the dead and quickening while the Son quickens without raising the dead.
3) It would seem that the "firstfruit" order found in 1 Corinthians 15:23 is currently operative, has been since His resurrection. See Romans 8:23 (… the firstfruit of the spirit); Romans 16:5 (… firstfruit of Achaia unto Christ.); 1 Corinthians 16:15 (… firstfruit of Achaia…); 2 Thessalonians 2:13 (instead of "beginning" read "firstfruit"). These all were vivified while they were living on earth and all have since died.
4) To determine if Christos should read "Christ" or "anointed" seems to be a contextual related determination, not textual. This is with the understanding that "Christ" means "anointed" whether translated as "Christ" or "anointed". Revelation 11:15 would have better understanding if "his Christ" were translated "His anointed", that is to say, "the Lord's anointed".
Study with verification