I like your post. You are think about the deeper things.

Isaiah's description of the Millennial resign did not exclude beast.

6 The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the young lion and the fatling together; and a little child shall lead them.
7 And the cow and the bear shall feed; their young ones shall lie down together: and the lion shall eat straw like the ox.
8 And the sucking child shall play on the hole of the asp, and the weaned child shall put his hand on the cockatrice’ den.
Isaiah 11.

It is to be understood that the millennium is for the righteous so the beast must have qualified to be there and so im very certain they will have a place in heaven. There is a purpose and a reason for everything under the sun.

The beast also have a spirit. This is my thought. I will comment other scripture references later. Thanks for sharing