Here I will be looking into a few different ways your items can be upgraded throughout different games. This can be weapons, items and abilities. As a secondary task I will be looking how they affect the gameplay if that feels relevant.
Bioshock 2 Weapon upgrades:
In Bioshock 2 every weapon you get has can be upgraded three times. The first two can be done in any orders but the third one has to be done last. In every case when a weapon is upgraded the actual weapon model is changed
The weapon I'm choosing to show as an example of the is the double barred shotgun its a simple weapon that is very self explanatory. It has a standard rustic feel for the the very steampunk style world but it does the job.
Once upgraded the barrel becomes sawn off to increase damage, the magazine is increased very visually making it easy to tell there are 6 rounds instead of 2 and the shells are electrified which is shown by having small Tesla capsule type objects attached to the side of the gun. Each of these make the gun statistically better as well as visually supporting the upgrade in that field. This is an amazing way to show upgrades in a game and I think it would be perfect for the style of upgrades I want to do with inventing (I'm think your could just handyman attach something to the gadgets you make.)
Ratchet and Clank Tools of Destruction Weapon Upgrades:
In the Ratchet and Clank franchise one of the main gameplay loops (in its most simple form) is shoot things and it upgrades your weapon, the concept art on the right shows that the developers can use the visuals of the upgrades as well as functionally to make the upgrades feel more rewarding.
In Ratchet and Clank tools of destruction, the rocket launcher the negotiator shows the upgrade in a very simple way the gun now holds three rockets in the magazine instead of three. The interesting thing in this case is that the whole colour scheme changes compared to your arsenal at the beginning of the game is full of yellows and bright blues very inviting colours but by the end is full of reds, navy and greys. both more threatening and menacing colours and for the theme of upgrading weapons they couldn't have done a better Job.
This is a good example of not just thinking of one aspect of the point you're getting across. don't just make them bigger or have more barrels but look more menacing as well. I think if I were to take anything from this is the item my charter would make may start quite hand made and show reading marks etc then have a better finish showing they have been worked on more.
Borderlands Pre sequel Wilhelm changes:
This Example is about Wilhelm's character model. After getting to a mid point in one of his skill trees levelling up an ability called 'power fist' will give your character a mechanical hand as an augment to your body. This actually changes the body of the model of the character you play as and this happens throughout the game.
The best thing about this example is it isn't just for the point of the gameplay and giving you abilities, this fills in a narrative gap as this is a character you see at a later point in the franchise (before this game came out) and in it he is practically 90% robot so it is narratively filling in the blanks of how and why he did this to his body.
Overall these examples give a lot of different aspects to upgrades within games, showing that it isn't just about the mechanical changes but also the everything else! The design of an upgrade builds on the narrative of the world its in and the more thought that goes into that design the more grounded in reality it is.