Contrary to what seems to be the general opinion here, this is not a huge problem. Actually, there are very few yachts in the true sense of the word that are concerned. But for some reason the question of life boats and their design has been attracting a lot of interest lately. I suppose it can be related to Octopus but we must not forget that Octopus is really one big exception to all that we have seen so far!
First, it's important to make the distinction between commercial yachts and private yachts. A commercial yacht is a yacht engaged in trade by carrying passengers for reward or remuneration (other than as contribution to the actual cost of the vessel or its operation for the period of the voyage or excursion). The typical commercial yacht is a charter yacht.
A private yacht is a yacht that is not a commercial yacht .
If the yacht used only temporarily as a charter yacht and for the rest of the time as a private yacht, it must comply with the rules and regulations for charter yachts during the period of charter even if it's only for a week!. That's one of the reasons why so many private yachts today are built to full MCA compliance.
The MCA code of practice deals with safety issues for large commercial yachts (24m load line length and over) and not carrying more than 12 passengers. MCA applies to the Red Ensign group (British registries) but is applied by other countries also.
A commercial yacht within the MCA code normally will not have to carry life boats. Only in the case of the yacht being 85m and over would this be an issue but in that case the yacht would also carry more than 12 passengers I suppose. Does anybody know a charter yacht being more than 85m carrying a maximum of 12 passengers?
Now we have the issue of commercial yachts being considered as passenger ships. This category is yachts carrying more than 12 fee-paying passengers. Most registries (and all the British!) will classify these commercial yachts as passenger vessels. A passenger ship on an international voyage must meet SOLAS passenger ship requirements.
I think most of you will agree that there should be no discussion about life boats on these large charter yachts ("mini cruise ships"). We are talking about Alexander, Turama, Sea Dream, Clelia II, Savarona, Christina O, Annaliesse, O'Mega, RM Elegant, Giant... Ugly or not, life boats are there because these yachts are PASSENGER SHIPS and the safety of the passengers is a very important issue - more important than the comfort of the staterooms and the number of Champagne brands in the wine cellar!
So, now we have the large privately operated yachts that will carry more than 12 non-fee paying passengers (also named owner's party or "guests"). There are not so many of these yachts around but we all know their names (Tatoosh, LGB, Pelorus, Lady Moura, Atlantis II, Octopus, Tueq, Al Salamah, Kingdom 5K...).
The question is not so simple to answer. Largely it depends on the flag state authorities. In some registries a private yacht carrying 13-36 passengers will not have to carry SOLAS-approved life boats (Bahamas). Some registries (like UK, Gibraltar) will demand full compliance to SOLAS and consequently life boats. Other registries (CI, Bermuda) tend to be flexible. We have all seen that Pelorus has no life boats, neither has Tattoosh. There are possibilities to substitute life boats by davit launched life rafts if the yacht complies to some other safety rules (2-compartment subdivision standard for instance). But this is looked upon case by case by the registries. We are talking about a very small number of yachts that are all unique!
Some yachts have been built to full SOLAS compliance carrying life boats. Octopus and LGB both carry life boats. But I suppose it's because they are expedition ships and the resale market is very small for privately operated ships of this category so they were built to full SOLAS compliance with the eyes on a future resale to the charter market.
Hopefully I have answered some questions - but as usual there might be new ones being raised so don't hesitate to post your reflections!