Explorers would be hit pretty hard, as it would turn long-range exploration into an actual survival game rather than simply tourism. Small journeys would be fine though, with a decent FSD a budding explorer could quite easily head out to a nearby nebula such as the Coal Sack, while further afield Nebulae around the 5000ly mark would be reachable with an AFMU or two. Only super-long distance exploration would require the full "living off the land" playstyle, which would add some much needed difficulty to exploration as it is pretty risk free at the moment.
Existing explorers and their stripped-down AFMUless ships would have to be considered, but that could easily be solved by simply only invoking the changes upon docking at a station to ensure that they aren't stranded. Alternatively, they could simply ask every player when they log in whether they wish to be teleported to the nearest station or whether they are happy with their current load out in the black.
The costs I mentioned were actually relating to the cost of outright buying the module divided by the amount of integrity it has, not necessarily the actual cost of repairing it. I just used that metric because the cost of repairing a module scales based on its buying price, so the buying prices can be used for direct comparisons for running costs. Considering how even the rebuy is only 5% of a module's cost, even an increased repair cost would likely be around 2.5% of the buying price to fully repair a broken module. This would put a Cutter down to 8.9K per jump with an A-rated FSD, which is minor on its own but can add up over time as well as the other modules would contribute additional operating costs. This is also assuming that module costs don't get a wholesale rebalance in the future to account for the ongoing income inflation.
Other professions would obviously draw their maintenance costs from different things gradually decaying during use. As you pointed out, combat has plenty of opportunities for a ship to break down over time as it places huge amounts of stress on almost every module other than the FSD; their FSD might emerge unscathed, but an intensive bout in a CZ might leave your thrusters, distributor, weapons and shield (and maybe other modules too) looking pretty worn out even if your shields never go down. Mining would be an issue, as you don't really do anything intensive that would place stress on the ship systems and core mining even places less stress on limpet controllers and the refinery than traditional mining on top of having completely crazy income rates, the only possible avenue of cost adding would be to make the seismic charges themselves very expensive to rearm; either way, mining needs a serious review on the profit it generates either way.
Ships can be used to have fun, particularly the cheaper ones. High operating costs would mean that players would want to use the smaller, cheaper ships to mess around in rather than their main flagships. If you want to go sightseeing or canyon racing, then do it in a DBX or Eagle rather than your Anaconda (plus, who goes canyon racing in a big ship anyway?). It would encourage players to mothball their flagships, letting their other, more efficient ships shine for the normal duties while the flagships get brought out for big events and tasks that a normal ship wouldn't be capable of doing. It's the same in any economic game, you use the cheap and expendable units/vehicles/tech when messing around and save the expensive stuff for actually getting stuff done. It's just like in real life how Destruction Derbys are a thing, but you will note that they always include a full roster of dirt-cheap cars rather than event organisers sending fancy supercars into the ring.
Elite dangerous, in the early days, used to be a game about economic survival. Every action you took had to be carefully considered regarding the risk/reward and, if you played the cards poorly, you could easily end a 6 hour session with less total wealth than you went in with even when you were trying to earn. Nowadays, you pretty much have to actively go out of your way to lose money.
