I've been down this road with my previous W212 E63. Bought it in Sept 2019 and by November I'd had the resonator removed (no secondaries on an M157) and had a remap at MSL. Apart from an LSD, it was perfect for me and I enjoyed 3 years of trouble free motoring.
Deciding to part with the car through lack of use 3 years ;ater, I advertised it on Autotrader and being honest, declared it had been remapped.
The first thing potential buyers asked was, did it have a FMDSH? I could answer yes to that, but some of the interested parties hadn't read the advert fully and thought the car was unmodified. On putting them right, every buyer bar one backed away.
So, with a sale at some point away, I will not remap a car again because instead of gaining value, it actually devalues it and makes it a far harder car to sell. I guess I could have remapped it , removed the map before selling it and claimed it was stock but to me that's dishonest. I wouldn't purposefully buy a previously remapped car, so why cheat someone else?
Now exhaust mods and visual ones like dechroming, lowering, LSD, different alloys etc I don't think matter when it comes to resale and may add value. But think hard about remapping a PPP car. Unless supercharging it, the gains are pretty insignificant hp wise IMO.