>>719200928
There's ways to acquire monster abilities through various methods
Though the most straightforward method is to make a Barbarian focused on grappling who goes into the Tyrant Totem line
At level 12 you can just swallow things like monsters can
And if you have the chops to learn an even more intricate system, you can try the third party optional rule system called Spheres of Power (or simply Spheres) as that one is far more flexible with far more methods of being able to gain the Swallow Whole ability

The fucked up thing is that the Tyrant Totem is first party Paizo
They know exactly what they've implemented