This actually seems to go against what you were saying earlier - that the share is only worth the portion of the market value of the aircraft, because you now seem to accept that the cash fund (Yes the term Engine fund has been used but I think most people who have been in groups accept that this fund is used for unplanned expenses of all types) adds value.
What you
do now seem to be saying is that a 1/4 share is NOT worth 1/4 of the market value of the aircraft (i.e. what it would be worth if sold on the open market) - this is actually a different argument from the one you have put forward before - are we getting somewhere now?
Also, if you buy your own aircraft and the engine goes bang just after buying you have to cough up ALL the costs, with no money having come with your purchase.