Now you can register to Kaiba Corporation for version 1.19. So I will give my fixes based on 1.19 system. Also YOU DON'T WANT 40 CARDS IN A GADGET DECK. I see in your post that you want to lower the number of cards in deck to 40. DON'T DO IT, FOR GOD'S SAKE. You need to draw ONLY 1 Gadget in your opening hand, to create the strong hand advantage you want. 42 Cads lower the chances of drawing more than 1 Gadgets in your opening hand and that's good.
OK, let's start:
MONSTERS:
-1 Jinzo (not good in Gadgets at all, since you need your traps for defense)
-1 Marshmallon (bad)
-3 Doomcaliber Knights (side them)
-2 D.D Assailant (inferior to D.D Warrior Lady)
+2 D.D Warrior Lady (doesn't need to get destroyed to activate her effect, unlike D.D Assailant)
+2 Thunder King Rai-Oh (always maxed. Stops the searching power of Sangan, Stratos, ROTA, Charge of the Light Brigade, Gladiator Proving Ground and Black Whirlwind, while it can negate the summon of Chaos Sorcerer, Bora the Spear, Dark Armed Dragon, Gale the Whirlwind, Cyber Dragon and Judgment Dragon)
+1 Blackwing-Gale the Whirlwind (staple. Halves the attack of an opponent's monster PERMANENTLY and helps your Gadgets kill anything. Gale can kill a Stardust Dragon just by itself. Also Gale + Gadget = lv7 Synchro or even better Gale + Breaker = Arcanite Magician, which either becomes a 2400 beatstick if you do not remove the counters, or it becomes a +2 if you remove them)
+2 Kycoo the Ghost Destroyer (very good for the new format, that Zombies, Lightsworns and Vayu Turbo will rise. Can help you get rid of Plaguespreader Zombie, Mezuki, Necro Gardna, Blackwing-Vayu the Emblem of Honour, the only 1 Gale that a Blackwing user has in his grave or even the 4th LS monster, in order to avoid a Judgment Dragon from being summoned next turn)
SPELLS:
-2 Shield Crush (the only monster people set nowadays is Ryko, Lightsworn Hunter)
-1 Creature Swap
+2 Shrink (helps your Gadgets win battles)
+1 Lightning Vortex (staple and very good against all those swarm decks out there)
TRAPS:
-1 Macro Cosmos (really bad and only in 1 copy)
-1 Bottomless Trap Hole (semi-limited now)
+1 Mirror Force (how could you forget this ?)
+1 Call of the Haunted (got unbanned now)
EXTRA DECK:
+1 Chimeratech Fortress Dragon
+1 Blackwing-Armor Master
+2 Arcanite Magician
+1 Black Rose Dragon
+10 more Synchros of your choice
Those where my fixes. Follow them and you will see the difference

Good Luck with your deck.