The footnotes for TAG troopers on p. 341 TO say that TAG only functions if it is assigned to a minimum of 2 troopers per squad, and that a maximum of 2 TAG troops can be assigned to each squad. The rules for TAG troops higher on the same page also specify, that TAG troops replace ordinary support weapons troopers.
What it seems to mean if I read it correctly (although it could be written more clearly - correct me if I'm wrong) is that:
1. You need exactly 2 TAG troopers per squad,
2. You can't assign any support weapons to such squad (as each TAG Trooper carries his own TAG, which replaces one of the two support weapons allowed per squad - see p. 150 TM).
What is confusing to me is if only one or all squads in a TAG Troopers platoon need to be equipped with TAG, and if all squads need to be equipped with TAGs what happens if I split the platoon into separate squads (using rules on p. 27 TO). Can each of the squads TAG a separate target each turn? What happens if I later merge those squads into a platoon? Can such platoon TAG only one unit per turn (whereas broken into separate squads it could TAG one unit
per squad)?
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Side notes:
1. The problem with number of units that can be TAGed by an infantry platoons broken into squads seems to also apply to spotting. The way I see it a conventional infantry platoon can only spot one unit per turn, unless it is broken into separate squads, in which case every squad can spot a separate unit each turn. Am I interpreting this correctly? Is this intentional?
2. If MegaMek Lab is correct, the only official unit of TAG Troopers is the TAG Spotter Infantry Stalwart Support-Spotter Infantry, which according to Master Unit List (
http://www.masterunitlist.info/Unit/Details/3149/tag-spotter-infantry-stalwart-support-spotter-infantry) appears in Technical Readout: 3085 Supplemental and Record Sheets: 3085 Unabridged — Cutting Edge. Since I don't have either of those, and the way MegaMek Lab displays it's data, I'm unsure if this unit carries 2 TAGs per squad, or only two TAGs per platoon (both in the same squad). I assume you have access to those pdfs, and I guess you could check them before answering if only one squad, or all squads in the platoon need 2 TAG Troopers for the platoon to be able to TAG to make sure if any answer you give or ruling or make about it does not contradict the number of TAGs listed for this unit in those sources (assuming the total number of TAGs per platoon is listed there) and if it does - you will know, that those pdfs need an errata.