Support coalesce of date fields

[DataOfficer]

I would like to coalesce date fields in Survey123. Is this possible? Explanation and use case described below.

Note: This was raised as a support case but I was referred here to suggest it as an idea (if coalescing of dates is not already supported).

I've produced a survey form using Connect, published publicly and accessed solely via the web form for submissions. The user is given three options of date entry (reason for this is given below):
Date (d/m/y), Month (m/y), Year (y)

Background calculations are then used to feed those results in to a single RecordDate field using coalesce functions (see below). These are all outside of a repeat (note we have had issues with coalesce functions within a repeat in recent support cases). The bind::esri:fieldType is set to esriFieldTypeDate. The feature is storing the individual date value (date_day, month_year or date_year) but not performing the coalescing function - leaving RecordDate blank. Testing without setting the bind::esri:fieldType to esriFieldTypeDate results in successful coalescing, but stores the output as a string rather than a date. As another workaround, is there a way we could convert this coalesced string to an appropriate date format?

The use case for this is we want a strong understanding of the accuracy of dates submitted with wildlife records. This is important for analysing phenology. 

Summary of XLSForm design of what we have tried so far:

type	name	label	calculation
date	date_day	Date
date	monthyear	Month & Year
date	date_year	Year
hidden	coalescedate1	Date (coalesced 1)	coalesce(${date_day},${monthyear})
hidden	coalescedate2	Date (coalesced 2)	coalesce(${date_day},${date_year})
hidden	coalescedate3	Date (coalesced 3)	coalesce(${coalescedate1},${coalescedate2})
hidden	RecordDate	Record date	format-date(${coalescedate3},'%m/%d/%Y')