For me, i'd personally like a a massive box set containing deluxe editions for EVERY Beach Boys album, and every major Live album and outtakes, demos, backing tracks, A Cappella versions etc. The tracks would implement the best stereo sources whenever possible. and i'd like to imagine a Mono Box Set of the earlier years as a counterpart. Pet Sounds and SMiLE would be 2-CD versions containing material from their respective box sets. The Party album would be the album + the original mixes and the best versions of the other tracks as featured on the newest release.
Having the backing tracks for the different albums as bonus tracks would also mean that Stack 'O' Tracks doesn't need to be in the set. Still Cruisin' would be the only release to have its original track-listing rendered, with the 60s songs removed and era appropriate tunes like Rock N' Roll To The Rescue, Happy Endings, Problem Child etc. amended to it.
This is something of a pet project of mine, but for example for Surfer Girl, Sunflower & Holland I would have:
Surfer Girl (Deluxe Edition)
1. Surfer Girl
2. Catch a Wave
3. The Surfer Moon
4. South Bay Surfer
5. The Rocking Surfer
6. Little Deuce Coupe
7. In My Room
8. Hawaii
9. Surfer's Rule
10. Our Car Club
11. Your Summer Dream
12. Boogie Woodie
==Bonus Tracks==
13. Back Home ('63)
14. Little Deuce Coupe (Demo)
15. In My Room (Demo)
16. Ballad of Ole' Betsy (Demo)
17. Mother May I
18. I Do (Demo)
19. Surfer Girl (Backing Track)
20. Catch A Wave (Backing Track)
21. In My Room (Backing Track)
Sunflower (Deluxe Edition)
1. Slip On Through
2. This Whole World
3. Add Some Music To Your Day
4. Got To Know The Woman
5. Deirdre
6. It's About Time
7. Tears In The Morning
8. All I Wanna Do
9. Forever
10. Our Sweet Love
11. At My Window
12. Cool, Cool Water
==Bonus Tracks==
13. California Slide (I'm Going Your Way)
14. Where Is She? (Demo)
15. Soulful Old Man Sunshine (writing session excerpt)
16. Soulful Old Man Sunshine
17. Walkin' (Demo)
18. Games Two Can Play
19. Back Home (1970 Version)
20. Sound Of Free (Mono Single Version)
21. Fallin' In Love (Lady)
22. Add Some Music (Alternate Lyrics)
23. Tears In The Morning (Alternate Version)
24. Our Sweet Love (Vocals With Strings)
25. This Whole World (A Cappella)
26. Slip On Through (A Cappella)
27. Forever (A Cappella Mix)
Holland (Deluxe Edition)
1. Sail On Sailor
2. Steamboat
3. California Saga: Big Sur
4. California Saga: The Beaks Of Eagles
5. California Saga: California
6. The Trader
7. Leaving This Town
8. Only With You
9. Funky Pretty
10. Mt. Vernon and Fairway Theme
11. I'm the Pied Piper [Instrumental]
12. Better Get Back in Bed
13. Magic Transistor Radio
14. I'm the Pied Piper
15. Radio King Dom
==Bonus Tracks==
16. We Got Love
17. Carry Me Home (Outtake)
18. Hard Times (Outtake)
19. Daddy Dear/Susie Cincinatti (Demo)
20. Sail On Sailor (Backing Track)
I would also fill in the gaps by having a disc highlighting the 1961-1962 sessions, a version of Landlocked to fit in between Sunflower and Surf's Up as well as the 70s Christmas Album, Adult/Child, Lei'd In Hawai as well as a CD of their last concert at Wembley Arena. (*hint* 'cause I was at that show

)
P.S I'd also like to thank Andrew for his wonderful website, as I wouldn't even be able to do this without it!