Poor wittle Spaess Mahreens have to suffer with their Vengeance Storm Bolters, Stalkers, Extended barrels, zombie grenades and debuffs that don't require the debuffer to put away the ranged weapon only their support class has. So sad.
Please, don't make the devs adopt the brainshit GW spawns these days. Also, someone told me they use Mk X armor, someone was too stupid to count there...(hint: the latest version is the Mk VIII Errant)...only proving the first point.
Yeah Mark IX is missing totally. Gone to Warp with Windows 9? These marines are easy to make though. Use the Mark 3 stuff, looks like the Mark 8 chestplate they haven and use Mark 4 helmet, and there, instant Mark 10 armour.
Sure LSMs can get Primaris Marines...... Only after Eldar(Sorry Aeldari) become Ynnari and get ALL OF THEIR UNITS.
For a logical lore based reason for NO, let's look at the circumstances. Ultrasmurf Marines appear after the rift opens, and Arkhona is supposed to be somewhere around the Eye of Terror. Basically in order for Primaris Marines to exsist in this game the planet needs to have been swallowed up my the warp rift... so GG Chaos victory, you're all daemon food. Except maybe the Orks who may be allowed to persist for the amusement of the Gods.