I don't think so, Logo. (Unlike Mormons who tend not to check out historic definitions of biblical concepts, but simply take their leaders at face value, I double-checked Lds.org):
The gospel is our Heavenly Father's plan of happiness. The central doctrine of the gospel is the Atonement of Jesus Christ. The Prophet Joseph Smith said, "The first principles and ordinances of the Gospel are: first, Faith in the Lord Jesus Christ; second, Repentance; third, Baptism by immersion for the remission of sins; fourth, Laying on of hands for the gift of the Holy Ghost" (Articles of Faith 1:4).
Lds.org glossary definition of 'gospel'
Now. Let's again "overlay" some of those non-existent Book of Mormon teachings to see if it fits this definition:
Lds.org says the Mormon gospel focuses on a "plan of happiness" -- what Lds writings have frequently called the "eternal plan of salvation." Certainly the "happiest" aspects Mormon writings focus in on is families living eternally forever with God.
(a) #5 & #15 supposedly detail (among other ways) how you do that. Subtract #5 and/or #15 from a Mormon's life -- say a never-married Mormon...or a non-temple Mormon...and they won't directly participate in the "happiest" aspect of heaven -- living eternally with Heavenly Father in the celestial kingdom.
(b) And do you also mean to imply that #4 -- exaltation -- has nothing to do with the Mormon "gospel?" Are you now saying that exaltation has NOTHING to do with the Mormon eternal plan of salvation that leads to supposed "happiness?"
(c) Lds.org also says: The central doctrine of the gospel is the Atonement of Jesus Christ. Are you now telling us that the non-Book of Mormon teaching of "Where in the Book of Mormon does it teach the blood of Christ does not cleanse certain sins?" has NO relevance to Christ's atonement? Really?
You remind me of the Scribes & Pharisees and all their dot and tittle!
look where it got them....
Excellent. The definition of gospel you found on lds.org is a good place to start. It identifies the Atonement of Jesus Christ as "the central doctrine of the gospel." The same glossary defines atone as follows:
As used in the scriptures, to atone is to suffer the penalty for sins, thereby removing the effects of sin from the repentant sinner and allowing him or her to be reconciled to God. Jesus Christ was the only one capable of carrying out the Atonement for all mankind. Because of His Atonement, all people will be resurrected, and those who obey His gospel will receive the gift of eternal life with God.
Note that these definitions make no reference to the many distinctive doctrines and practices of Mormonism that the original article mentions: eternal marriage, temple work, the Word of Wisdom, and so forth.
I admit that many Mormons use gospel as a synonym for all of Mormonism; but such usage is imprecise. As used in the Book of Mormon, the gospel is the "good news'' of Jesus Christ: He atoned for the sins of the world; He arose from the dead on the third day; and He has provided the means whereby we may be cleansed from our sins and enter into the kingdom of God. (See 3 Nephi 27:13-21)