Presumably, BioWare is working on another Mass Effect game, that will either be a sequel or a prequel. I would prefer the former, and if it were as such, I would be pleased to see the game incorporate aspects of its predecessors. (N.B.: This is a bit long, so I'll break it down into multiple posts).
In this part: Armaments and Inventory
Next part: The Protagonist, Prior History, and Non-Combat Interactions
~Weapons, Armour, and Inventory~
The M-7 Lancer from the Citadel DLC, the Particle Beam rifle, and the Collector weapons prove that the 'old tech' weapons can work in a ME3-style combat setting. I would like to see the return of the inventory system from ME1 (on the PC). I know that many people disliked this, but inventory management is a key part of virtually all RPGs.
However, rather than finding 'X Weapon I-X,' the guns could be organised along certain 'lines' or 'patterns.' For example, assault rifles of the Vindicator pattern would be burst-fire guns that always require thermal clips, with preset firing modes of 2-5 rounds per burst. 'Avenger' pattern rifles would have optional thermal clips, and resemble the M-8 Avenger/M-7 Lancer in appearance and function, etc. Guns that fire explosive rounds, large flechettes, or other non-standard (and lore-breaking) ammunition would be put in their own category, perhaps as 'Exotic' weapons, and would be harder to find, and probably not available from most merchants.
Why would one select to use thermal clips and essentially have limited ammunition, when a gun can use either system? Well, usage of thermal clips would occupy a mod slot, but would provide boosts to damage output and ROF (as claimed in the ME2 codex). Additionally, environmental conditions and hazards (as seen in ME1) would affect weapon performance, with hot environments causing 'old tech' weaponry to overheat much faster, or even malfunction.
I would like to see the return of the omni-gel recycling system, allowing the player to break down unwanted gear or items, and use the omni-gel for repairs and other tasks.
Armour should be customisable and modular, a la ME3. There should be set patterns, and perhaps even bonuses for making a complete set from one line or manufacturer. Ideally, but not realistically, wearing certain armour sets with the proper colurs could influence NPC reactions. E.g. wearing a set of Cerberus armour with the associated colour scheme (bone white, with black and gold trim) would provoke comments from NPCs, and elicit favourable reactions among some humans, and hostile behaviour from some alien individuals, and even serve as a disguise in some capacity. However, wearing this armour with a woodland camo scheme would not have any effect on NPC interaction, besides comments like 'Nice armour!' 'Looks heavy,' etc.
I always found it a bit odd that no one in ME3 has any issue with Shepard wearing Cerberus armour, with their emblem and colours proudly displayed.
In fine, I would like to see the following features from the prior ME games.
ME1: Omni-gel, inventory system with weapon quality, environmental hazards. ME2: Customising squad's loadout from one terminal, as opposed to running between different lockers. Thermal clip weaponry. ME3: Weapon modification, combat system, armour customisation