Just to add some suggestions to your list , also hoping to add whatever is added in s9 
(not everything is here, only the items that could have some difference)
-Grenade: post s1 design, old sounds and effects (should be applied to the already existing s1 grenade), aimable, compared to regular grenade higher damage (100), higher structure damage (375), higher max stack size (10), stats from 6.21 could work.
-Slurp Juice: 1 effective health per tick, 75 in total, higher duration, lower max stack size, can be thrown and used while moving.
-Impulse grenade: almost identical to the original, it would have it’s old sounds and animations and, for making it different, higher max stack size (9).
-Suppresed Pistol: old sounds, taking only note of RARE and EPIC rarities, although there’s stats for a LEGENDARY variant that was added after EPIC and LEGENDARY converted. Higher EPIC player damage (28), higher structure damage (27, 28), higher magazine size (16), faster reload time, semi-automatic.
-Chug Jug: old textures, allows to move while healing but doesn’t heal progressively like Legacy version, can be thrown.
-Minigun: old sounds, it could have less player and structure damage with 1.5x headshot multiplier but no overheat bar.
-Crossbow: lower player damage (75, 79), significantly lower structure damage (1). Same for cupid crossbow and it’s RARE ratity, not added.
-Handcannon: old design, lower player damage (75, 80), higher sprinting spread, higher jumping/falling spread multiplier.
-Hunting Rifle: just to have it’s old icon and sounds and therefore it’s corresponding stats. Higher RARE player and structure damage (91), slower reload time, lower headshot multiplier, slower projectile speed.
-Light Machine Gun: higher magazine size (100), slower reload time, higher headshot multiplier, lower fire rate.
-Port-A-Fort: only thing that could be added from this is it’s EPIC rarity, which only difference is it’s max stack size (5), but worth noting.
-Remote explosives: old design and sounds, slightly lower player damage, higher drop count (4), higher stack size (10), smaller floor mesh, lower structure damage, doesn’t beep. Could apply to the RARE rarity, so, according to 3.30 stats, it would have less damage radius and throw distance, increased delay between sequential explosions and increased delay before detonating a charge or throwing another one. It EPIC rarity was added to, it could have it’s 5.40 stats.
-Thermal Scoped Assault Rifle: old design, full automatic, higher player and structure damage, (36, 37), lower fire rate.
-Drum Gun: higher player and structure damage (22, 23), lower fire rate, higher headshot multiplier.
-Dual Pistols: old sounds, taking only note of RARE and EPIC rarities, although there’s stats for a LEGENDARY variant that was added after EPIC and LEGENDARY converted. Lower player damage (41, 43), higher structure damage (42, 44), lower fire rate, slower reload time, higher headshot damage. As a suggestion for making them unique, make the fire type semi-auto, as the description of the weapon stands.
-Stink Bomb: EPIC rarity could be added for this one, making the already existing RARE have lower max stack size (5) and the EPIC higher (6), and EPIC having current OG stink bomb stats (higher damage and duration).
-Submachine Gun: old design and sounds, using 5.10 icon because it was last seen in 7.30, therefore i’m mentioning it’s stats in that update. Higher player and structure damage (17, 18, 19), lower magazine size (30), higher headshot multiplier, slower equip speed, slower ADS speed.
-Compact Submachine Gun: old design and sounds, using the first icon for differentiation. Comparing to actual compact submachine gun, higher player and structure damage (20, 21), higher magazine size (40), lower fire rate, slower reload time, higher headshot multiplier.
-Double Barrel Shotgun: lower player damage (114, 120), lower headshot multiplier, no max damage cap (important), old pellet spread.
-Rift-To-Go: slightly larger icon, principal difference is you can pick items while using it so you take them before it activates and rifts you into the sky.
-Shockwave Grenade: just old sounds and effects, not important.
-Suppressed Assault Rifle: old sounds, lower fire rate, higher spread, higher headshot multiplier.
-Heavy Sniper Rifle: higher player damage (150, 157), significantly higher structure damage (1050, 1100), lower fire rate, higher reload time, no sniper glare.
-Grappler: only notably difference it’s the activated fall damage when used. It could also have 15 uses like it used to.
-Birthday Presents!: old design, higher health bar of surfaces, lootbar of 9.41
-Ballons: EPIC rarity could be used to add the now deprecated utility of these before the rework in 7.00. Higher max stack size (20), max of 6 ballons can be used at a time with the condition you have to equip the item without being able to equip anything else. ADS would also release a ballon. Ballons with emote icons would appear sometimes
-Havoc Stones: not sure of the reason of it’s existence, but still an addition.
-Six Shooter: only old sounds, not important.
-Quad Launcher: old textures, able to rocket ride, not important.
-Fiend Hunter Crossbow: lower player damage (40), not important.
-Pumpkin Launcher: although a “legacy version” already exist, it can be replaced with an OG version with the rarity grid, old sounds and old stats, just like the heavy shotgun. Counting also RARE rarity, higher player damage for RARE and EPIC (110, 116) and lower for LEGENDARY (121), higher structure damage (375, 394, 413), faster reload time, lower recoil, higher recoil recovery speed.
-Heavy Assault Rifle: old sounds and icon. Taking only note of COMMON, UNCOMMON and RARE rarities, although there’s stats for an EPIC and a LEGENDARY variants that were added after RARE, EPIC and LEGENDARY converted. Higher player and structure damage (38, 40, 42), higher headshot multiplier.
-Scoped Revolver: no sniper glare, not important.
-Gliders: would be cool to have these because of the old design.
-Snowball Launcher: old textures and sounds, as said with the grenade launcher, projectiles bounce rather than just explode in the impact, higher player damage (100, 105, 110), higher structure damage (375, 394, 413), higher magazine size (6), higher fire rate.
-Presents!: old sounds, 7.10 lootpool, not important.
-Infantry Rifle: old sounds, semi-automatic.
-Flint-Knock Pistol: old sounds, hitscan, does not cancel damage when used mid-air.
-Buried Treasure: honestly surprised this one hasn’t been added yet. It could be good having a BR variant with variable lootpool and an OG variant with 8.01 lootpool and the black cross.
-Egg Launcher: old design, textures and sounds, higher player damage (100, 105, 110), higher structure damage (375, 394, 413), no swap delay between launchers.
