I'm sorry sir, I disagree.
To me, election is to salvation ( 2 Thessalonians 2:13, Ephesians 1:4-5, Romans 8:28-30 ), but I do agree that it is for a purpose.
I'm reminded of this passage when I read your quote above:
" Now I say, [That] the heir, as long as he is a child, differeth nothing from a servant, though he be lord of all;
2 but is under tutors and governors until the time appointed of the father.
3 Even so we, when we were children, were in bondage under the elements of the world:
4 but when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law,
5 to redeem them that were under the law, that we might receive the adoption of sons.
6 And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father.
7 Wherefore thou art no more a servant, but a son; and if a son, then an heir of God through Christ." ( Galatians 4:1-7 ).
Jon,
The above tells me the following:
1) The example is given that the heir, as long as he is a child, does not differ with a servant of the household though the heir is ( and will be ) lord of all in that household.
2) The heir is also under tutors and governors ( teachers and overseers ) until the time that their father's appointment becomes a reality and they assume their role.
3) Believers, when they were children ( did you catch that? Believers in Christ are yet children even before they are made aware of their salvation, that is how I read it ), were in bondage ( servitude ) under the elements of the world.
4) When the fulness of time was come, God sent His son ( made of a woman, made under the Law of Moses )…
5) To redeem them ( the elect ) that were under the Law...so that we ( those that would believe, His elect ) might receive the adoption of sons.
6) And because we ( the whosoever believeth, from the heart ) are sons ( not "will be" ), God has sent forth the Spirit of His Son into our hearts, crying, "Abba, Father".
7) We, as God's elect are no more servants, but sons. If we are sons, then we are also heirs of God through Christ.
In other words, I don't see this passage describing what I've underlined in your quote above ( a "will be" with respect to becoming an heir ) or becoming ( to go from being one to the other ) sons of the household;
But we "already are" when it comes to being part of God's household, even before we have believed.
What do you see when you read this passage, if I may ask?