The General System.
In Bioshock: Survival the weapon system is largely unchanged. However, with the revival of the U-Invent, several new options come into play. You can now break down ammo and other objects into their basiv U-Invent parts. You can also invent new ammo types and certain gene tonics (Duh) You can also invent inhancements. These are attachments for the weapon, but have effects that are much less drastic than Upgrades that you can get at Power to the People stations. They include things like different skins for weapon appearance, certain attachments that add asthetic appeal, and other tidbits that further distinguish your character.
UpgradesThe upgrade system has been majorly revamped. Instead of finding a Power to the People station and getting a permanant upgrade, you'll find Upgrade tokens. These tokens can be put into a PTTP machine and spent for upgrades. If you don't like an upgrade, you can get it refunded once, and spend the token on another upgrade. I do this for two reasons: 1: Ricochet upgrade for the minigun. and 2: What if you change your playstyle halfway through the game? This way you can be somewhat flexible. The tokens are as hard to find as the PTTP machines were. They can be on Bosses, hidden in obscure locations, or have a shrine to them in some crazy splicers place. They really can appear anywhere, but are rare.
And for the upgrade system? Well i got rid of the annoying list of confusing upgrades, and added a wheel of six different upgrades. Each Upgrade is a certain primary color, (red, blue, yellow). Each Final Upgrade is a secondary color (purple, green, orange) Getting the corresponding mix of primary upgrades unlocks the final Upgrade.
DISCLAIMER: Willbachbakal posted this system first. I came up with the idea before i read his blog. So sue me.
That's about it for the weapon mechanics. What do you think? and Willbachbakal please don't be mad, i actually did come up with the system. I was surprised too when i read your blog.