On this post (here), I have numerous links to posted research linking the "great crowd" to the New Covenant and the Abrahamic covenant, as well as a Scriptural refutation of the Society's linking of the '10 gentiles grabbing hold of the skirt of a Jew' (Zech 8:23) and the 'Egyptian slaves' of Isaiah 45:14 to the great crowd.
Hope this proves helpful.
On the Society's linking of the 'covenant for a kingdom' in Luke 22:28-30 with the Lord's Evening Meal (Luke 22:19, 20), I find it interesting that they insist that the kingdom 'covenant' of verses 28-30 is directly related to the partaking of verses 19, 20, yet they also insist that Luke's presentation of verses 21-23 (which, by the order presented in Luke, would have Judas as a partaker of the emblems) is not chronologically accurate.
They pick and choose what they want as 'evidence,' and disregard what they don't like.
Take Care