In order to safely operate F-35B's from a ship, there are a number of design requirements or modifications which would need to be made. Something which IMO should not be automatically assumed even with a vessel of 25,000 tons.
The first is whether or not there would be sufficient clearance around the aircraft for takeoff and landing. Given the ship would likely be carrying some helos, the clearance issues are likely to relatively minor. What are not likely to be minor issues are whether or not the deck can handle to weight of an F-35B and/or the heat from the engine. With respect to weight, the empty weight of an F-35 is ~13,000 kg, which is ~5,000 kg more than the loaded weight of an SH-60/S-70B Seahawk(~8,000 kg), a loaded F-35 is ~22,000 kg, and a fully-loaded one is ~31,000 kg. Unless the deck is designed to handle that sort of weight, or modified to handle the weight (with the significant amount of weight and structure dedicated to do so) the an F-35 would cause the deck to collapse, likely destroying the F-35B in the process as well as causing serious/mission-kill damage to the vessel. Similarly, the deck needs to be able to handle the heat put out by the engine on (vertical) takeoff and landing, otherwise there could be simiar issues to having a deck not rated for that level of weight.
Then there is also the little matter of how many F-35B's a carrier needs to be able to operate to provide a useful capability, what they need to be able to carry in terms of stores, and sortie generation rates.
Basically, unless the vessel is designed from the outset to operate jet fighters like the F-35B, it might be possible to modify it to do so, but it also might not make any sense to do so.
-Cheers