We believe confession and belief ARE sufficient for salvation (Romans 10:9) and salvation is not dependent on human works (Ephesians 2:8,9). Confession and belief are sufficient to keep one from hell.

Jesus surely demonstrated this with the thief on the cross. 1 Corinthians 3 makes it quite clear that Christ is the foundation and that what is built upon it will be tried. The works of him who has laboured in vain will be burnt up, but he will be saved, “yet as though through fire” (vv.13-15). We believe that one can accept Christ and not make much headway on the path to maturity and yet still inherit eternal life. Is it the ideal? No. Is it what Christ wants? No. Do we pursue this as a model? No. Are babes in Christ (the first part of 1 Cor 3) denied entry to the Kingdom? No.

I agree with your main point though: The gospel IS more than a get-out-of-hell-free card. Discipleship is key to the gospel.

Holiness, godliness, the fruits of the Spirit, and maturation to produce “good fruit” come via discipleship, hence Christ’s insistence upon it.

Discipleship is the model for advancing the gospel and growing the Kingdom. It is discipleship that helps the babe in Christ to realize that grace is not a license to sin the more (Romans 6), that there are greater depths of relationship with God to be realized, that his plan of salvation is not just for me/you, etc.

But discipleship is a building block on the foundation of faith in Christ. It is not THE foundation. I think we need to be careful to delineate that which is a requirement for salvation and that which is the Biblical approach for maturation in the faith and the spreading of good news to the lost.