The idea is fairly straightforward, having played with AT rifles a bit more, I have come to really enjoy using them against infantry, and wish to have more opportunities to do so beyond the AT gunner class. Ideally as well, it would be nice to do so without sacrificing the secondary slot on an AT rifle in campaigns where the option for an AT launcher exists, but given the very extreme nature of such weapons (slow, cumbersome, but very high damage that keeps at range), I believe these would be best suited to being made event weapons.
There are candidates for such a weapon across multiple factions and campaigns, so I’ll list off some example candidates.
Firstly the Type 97 AT rifle. Found already in the Pacific campaign, it served as the basis of the Ho-1 and Ho-3 aerial cannons, from which eventually came the Ho-5. Consequently, the Type 97 is compatible with Ho-1 and Ho-3 ammunition, including high explosive tracer, high explosive incendiary, and incendiary tracer.
As a counterpart to the Type 97 for the Pacific campaign, the American Winchester-Pugsley anti-tank rifle would be a welcome candidate, boasting semi-automatic fire and a 10-round magazine. This rifle would be compatible with M23 incendiary.
For both Germany and Italy, the Solothurn S-18/1000, under the names 2cm PanzerabwehrbĂĽchse 785 (s) and Fucile anticarro tipo S respectively, offer a similar experience to the Type 97, with 5, 10, and 20 round magazine options, as well as being compatible with Flak 30 and KwK 30 ammunition.
For the Soviets, the PTRS-41, already found in Soviet campaigns, I believe should be compatible with 14.5x114mm ammunition, which includes a multitude of explosive and incendiary options.
Overall this is mostly just a suggestion built on the grounds of “wow, these weapons sure are fun”, so the goal would be to keep any potential introduction of them in the spirit of that sentiment. Any suggestions for weapons I missed, ammunition options not considered, or concerns are all greatly appreciated.