I kind of want to see a 14.5mm caliber antimaterial rifle developed, using modern ammunition. It may prove impractical, but they should at least attempt it.
The south africans have a rifle that combines a 20mm cannon round and a 14.5mm round option... just change the barrels and swap between the two calibres.
the 20mm is effective to 1,600m with HE rounds being quite powerful and effective against a range of targets, but the 14.5mm barrel is used against armoured targets out to 2.5km with its higher velocity making it more effective out to much greater range than the lower velocity 20mm round.
I have often mentioned on this site that a Russian rifle using the 23 x 115mm round currently in use in the Russian military (the Mi-35Ms with chin mounted 23mm twin barrel guns use this round as standard), and the 14.5 x 114mm round of similar size could be used in the same combination.
A modern SLAP round for the 14.5mm round would have impressive performance... a 15mm calibre weapon developed in Europe in the 1990s had the ability to penetrate 40mm armour at 1km using a similar round and it was based on the 14.5mm round.
More importantly a 23 x 115mm round would have a combination of a heavy HE projectile (same projectile as fitted to the anti aircraft 23 x 152mm round fired by the ZU-23 and ZSU-23-4) but the wider calibre should allow more energy to be pushed down it meaning a SLAP round in 23 x 115mm might be even more powerful than the 14.5mm version.
Keep a barrel for both and perhaps extra smoothbore barrels for the APFSDS rounds and you would have an impressive weapon that uses standard in service ammo...
The 14.5 mm is an overkill for the role; therefore 12.7 mm is tactically superior due to its lighter weight (round and rifle).
For certain uses the fact that the 14.5mm generates twice the energy at the muzzle than any 12.7mm round makes it attractive and interesting... shoulder fired anti helo rifle anyone?
Perhaps with a backup short barrel 40mm grenade barrel for the caseless Balkan grenade launcher effective to 2.5km, or a 23 x 115mm barrel effective to 3-4km...
With modern external weapon mounts having a dual feed rifle with HE and APFSDS rounds for soft and hard targets and the electronic sight and software to allow for their very different trajectories would make a very powerful weapon system...