What is being described in this topic-thread does not sound like long-term investing.
The average buy price of the entire number of units of a scrip is useful to know as one’s “entry-cost” ONLY if one intends to liquidate all the units of a scrip. Otherwise that number is unnecessary noise/clutter and misleading.
Also, the average buy price of the number of units of a scrip that one wishes to sell is a fairly static number, doesn’t need real-time monitoring.
That’s what the Holdings page already shows.
If one is interested in these aspects,
then one can simply keep viewing the Holdings page, no? 
Am still unable to see the utility of this feature-request for long-term investing.
The average buy price of how many units should be shown?
if various units of the scrip are purchased at different prices over time, the average buy price depends on the units that one is selling. Displaying the average buy price of the entire holding of scrip doesn’t sound useful when one only intends to sell part of it.
As far as the utility of such a “feature” for trading in concerned, maybe others can chime-in, and make a better case for it. So far, to me, it sounds very much like clutter at best, a misleading number most of the time, and at worst a dark-pattern designed to encourage over-trading (though the intention behind this request might not be do so).