We might think so, but in the final analysis the judgement is likely to be made on the seller's claims of what it is suitable for, not what buyers might want it to be suitable for.
Not a comment made to be argumentative but a flag that if seeking redress for something not offered, failure is likely to follow.
By comparison, there are brands that make "all season" use a selling point, this rather suggests its not a given for all caravans.
I am a bit concerned that in your case condensation has played a role and will be fronted by the seller's defence, as an aspect not wholly in their control.
As you seek, you do need the services of a competent expert to identify where all the issues causing the mould etc lay. If primarily it is physical leaks, then your chances are way better.
All said, I wish you luck.
further to this point, In UK law it is the buyer who should verify the product on offer is suitable for the purpose they intend. Consequently as a buyer you need to ask all the questions before you decide to buy a product.
Whilst the law says you should be able to trust the information a dealer supplies about a product, for example the information in an advert or a brochure they use and any verbal information they supply, the law does not require them to provide all the information, but what information is supplied must be accurate. This is frustrating especially for a novices who might not know what questions to ask, but here again the Law takes the view that a dealer who sells a product should use his specialist knowledge and experience to guide customers to make the best choices.
That is why a good dealer will engage with the customer and try to ascertain the customers expectations for the product and their likely usage of the product. The dealer should then use their knowledge to point out any glaring or important mismatches so the customer can make an informed decision.
It is in the best interests of both the customer and the seller that all parties agree the product is well matched to the intended purpose the customer has indicated.
It should also be noted that if a dealer/seller becomes aware that a customers expectations or stated use is incompatible with the product, they can refuse to sell it, thus preventing on going warranty claims or breaches of contract.