The arrangement also has the benefit that the group are able to reclaim VAT on all fuel purchases , repairs, maintenance and all other vatable expenditure on the aircraft . The disadvantage of course is needing to charge VAT on group invoices, but assuming that the group is non profit making, then it is an entirely revenue neutral operation.
It's usually slightly worse than revenue-neutral as no VAT is chargeable on insurance and it's often not worth reclaiming smallish amounts of VAT on e.g. fuel bought in other EU states.
The advantages are in capital outlay, and if your hirers are themselves able to reclaim VAT.