The ability to calculate unrealised gains at a past date would be valuable to me.
When submitting Superannuation annual report & distributing profits to funds to members, it is necessary to calculate investment unrealised gains at the end of that financial year (a past date). If more shares have been purchase since the end of the financial year, Manger’s unrealised gain calculation can not be used as in includes shares purchased after the end of the financial year.
This could be addressed by simply reporting the unrealised gain give a share price and an optional as at date. That value could then be entered into an appropriate journal entry.
Another solution would be recording a series of share price date pairs then Manager posting corresponding values to a Balance sheet account and Profit & loss account. However this later approach sounds more complicated and may need more explicit support to varying jurisdiction requirements (which I’m not aware of).