Go back to my previous comment. The engine fund belongs to the engine overhauler.
What rot - If this were the case you would have to have this fund as a private owner and pass it on to the buyer (or to the engine shop) when you sell. With whole ownership you just put any fund in your pocket - with a group this does not happen, the fund stays with the aircraft - and the new share owner needs to pay for it.
As far as liability goes, the liability for the new engine is there with or without the fund and is why the same aircraft costs (say) £30,000 with a new engine, £28,000 mid life and £25,000 time expired, and I STILL cannot see how you can say the share is worth the same with or without the fund.
(And you did not say which share
you would have gone for Bose)