How can a 3rd place team be more deserving than a team that finished 2nd? Are you really suggesting a team that is beat in the play offs after finishing 2nd is less deserving than a team that finished 3rd?
If you take a close look this new WCQ via UEFA. It is completely different to anything that's ever occurred. For example, in this insane format, WCQ consisted of 6 4-team groups and 6 5-team groups. So we don't even have the same number of teams in each group. So it's now unbalanced to begin with, before we even get into the new qualifying process. In this format, we have a situation in which a 3rd place finisher in a 4-team group (Northern Ireland) has advanced to the playoff over multiple 3rd place finishers in both other 4-team groups and in many 5-team groups due to their pre-WCQ Nations League ranking.
You seem to be under the impression that 3rd place nations
haven't already advanced to the playoff over arguably more deserving 3rd place finishers in other groups, many in larger groups, where it's even harder to finish in the Top 2 than in a 4-team group. This new WCQ unbalanced "selection" process is completely unlike anything we're ever seen. It's the first time anything like this has ever happened due the larger World Cup, but the way they've gone about only compounds the problem. On top of this brand new format, we have a situation in which they now need to find a replacement!
So we
already have a situation in which multiple 3rd place finishers (some in 5-team groups, 1 in a 4-team group - NI) are in the playoff based on their Nations League ranking. So these members finished 3rd and have an opportunity to make the World Cup. Ask yourself, in a situation in which a replacement is needed, why shouldn't other 3rd place finishes (the next best finishers) get an opportunity now that Iran will not be competing? We now face the possibility of an additional 1 or 2 slots (Iran and possibly Iraq) will open up. No one seems to have any clue how FIFA will decide these replacement spots.
If your argument is that the replacement nation should come from a loser of a playoff, is that really what you want, and how would you decide which playoff loser to choose and why would you choose any playoff loser over another 3rd place nations who didn't get a playoff opportunity? Why would put the loser of the playoff in over another 3rd place finisher who didn't get that opportunity but may have done as well or better in WCQ? They already have their opportunity, other 3rd places finishers have not gotten this opportunity so they should now get one.
So please think about this deeply - We already have multiple 3rd place finishers (1 in a smaller 4-team group) who made the playoff based on a pre-WCQ ranking through a brand new unbalanced group WCQ system consisting of half 4-team groups and half 5-team groups. Ask yourself, why should some 3rd place nations have made it into a playoff while others not? Not based on WCQ but a pre-WCQ ranking. With some nations competing under a different set of criteria and in different sized groups we have a completely nonsensical selection process.
Now we're looking at 1 and possibly 2 openings. Really think about what would be the fair thing to do - wouldn't it be important to give the 3rd place finishers who
did not receive a playoff opportunity despite in some cases performing better in WCQ with more difficult competition within the group than the 3rd place finishers who are in the playoff.
If it matters to you where you finish, in the Group, lets say Italy defeats Northern Ireland in the playoff. In that scenario are you more willing to give another 3rd place group finisher an opportunity over Northern Ireland since NI was a 3rd place finisher? The fact is they finished 3rd in a 4-team group over others who finished 3rd in a 5-team group. But what if Italy lost, since they finished 2nd, then what? Then you wouldn't replace them?
To replace Iran, I would favour an additional playoff between the best of the 3rd place UEFA finishers who did not advance to the playoff normally, and UAE the next best AFC. That said, I have no idea what's going to happen but I have no confidence in FIFA for making a good decision because they've already shown us how disorganized they are with this crazy new WCQ system that has "chosen" certain 3rd place teams (often in easier or smaller groups) than other more deserving 3rd place teams. And now you're saying we can't take any 3rd place team over a 2nd place team, even one already in a playoff?
No one seems to have any flipping clue what is going to happen to replace Iran and I would like to see some clarity from FIFA about what is going to happen. I think the best thing you do is you put the best 3rd place teams who didn't make the playoff in with each other and UAE and play it out for the final spot(s), unless you have a better idea - in which case make your case and lets have a reasoned discussion about it please.