That sounds like an interesting concept, but I'm not sure that I fully understand the application (or that it gets the team what it wants).
If I understand the team correctly, they can have a group of articles/projects for a given magazine in process at the same time. The templated workflows use Start Date as the schedule mode (as it may not be immediately known into what issue an article will be slotted). Once the issue date is assigned, the team then wants to see if that project is tracking to the issue deadline (if the project is running late, the team may decide to bump the article to a later issue).
As an example, if the issue date for Magazine Alpha is July 2023, then the issue deadline is 6/6/23 (the first Tuesday of the preceding month). We would likely build a report to show all Magazine Alpha projects slated for July 2023 and indicate if they're on track to complete by 6/6.
I found a Fusion guide for calculating the nth day of the week in a month and tweaked it to try and create calculated fields in a custom form.
I created a test custom form with two dropdown fields--'TEST Issue Month' (with month names as the labels and numbers--'01','02', etc. as the values) and 'TEST Issue Year.' I then created two calculated fields:
TEST Issue Date Preceding Month
CONCAT(({DE:TEST Issue Month}-1), "/01/", {DE:TEST Issue Year}, " 5:00 PM")
TEST First Tuesday Preceding Month
ADDDAYS({DE:TEST Issue Date Preceding Month}, 1 * 7 - DAYOFWEEK(ADDDAYS({DE:TEST Issue Date Preceding Month}, -3)))
(I tried combining the calculations into one field, but the time value came out wonky.). This seems to work--the second field yields Jun 6, 2023 5:00 PM--but I don't see any way to account for holidays.
This is a long-winded way of saying that it may make the most sense for us to just create a deadline field that the users have to manually enter.