Fair enough. Perhaps it could be a track option. Im not prepared to say that making item pickup information transparent would be bad though...it would just make the game different.
Enable/Disable: Viewable/Color Coordinated Item Pickups.
Whether or not this would add or detract from the game, is up to the developers. I, for one, look forward to participating in the Early Access feedback
I do really like the 'rapid mine detonation' for speed boosts idea.
My caveat with the mine limiter on how many mines there are is that it could create a rather inconsistent experience for other racers.
For example, if you're in 2nd place approaching a 1st place opponent on the final lap, and they are on a direct line to an approaching mine....it would feel rather un-fair & un-lucky to have that mine suddenly disappear or have no affect. The opponent in this case would maintain the lead not by skill or execution, but by sheer luck that another racer took it upon themselves to randomly deactivate their old mine absent the knowledge of it almost being rendered effective on a racer. A race would feel more like a roll of the dice in these cases...and I'm willing to bet that this could happen rather often (or perhaps rarely, but still often enough to be noticeable and annoying)
Many of these suggestions are great from a first person game-play point of view, but they may have ramifications to the gameplay...and it's important to not only think of cool weapons/features, but also proper ways of implementing them.
In this case...I think a possible proper way to implement this 'mine limiter' idea, would be to ONLY allow a racer's mine to be disabled or brought out of rotation after completing another task, or make it contingent upon something else. Maybe they can only remove a mine after lapping said mine, so that it has a chance to have an effect on other racers. Perhaps you're approaching a 1st place racer on the final lap and you are desperate to have extra mines to prevent the 3rd place racer from overtaking you...but you are already at your limit and need to wait to pass your prvious mine before an available mine slot becomes available. I don't think something like this would make the game less fun, I think this would simply add a layer of strategy to weapon deployment and inventory management. Lay as many mines as you can? preserve mine slots for certain parts of the track? Save mines for the end of the race?
In addition, having extra weapon deployments for each weapon could offer alternatives to racers if they have reached their limit on mines. If a mine can be projected forward as an unguided missile...this at least gives a racer at their mine limit the option of still being able to deploy their mine in an offensive way without simply ejecting the item that they cannot use due to an arbitrary mine/weapon limit imposed on them by the game.