Preserve code blocks ('xd:preserve') not supported in InfoPath Forms Services

See Readonly display of MultiLookup value in InfoPath Forms Services: my initial approach was to handle this in the InfoPath template itself, via Custom XSLT:

That approach works when testing in InfoPath Designer - preview.

However, upon publishing the template to SharePoint my custom XSLT is lost. Microsoft in MSDN article Using Custom XSLT in InfoPath Form Templates states that you can protect your XSLT customization for overwriting via 'xd:preserve'. Indeed with that inserted, upon saving the template the customizations are preserved:

However, I ran into another issue that Microsoft does not make clear in the referred MSDN article: forms with preserve code blocks in it cannot be published to SharePoint.

Hidden in other MSDN article Creating InfoPath Form Templates That Work With InfoPath Forms Services it states that 'XSLT extensibility (xd:preserve blocks)' are amongst the 'Features with No Direct Parallel on the InfoPath Forms Services'.

Note that you can [still] apply Custom XSLT in InfoPath Forms Services context, the limitation is that code preservation is not supported. So on every save in InfoPath Designer, the custom XSLT code blocks get overwritten, and you would have to insert them again. That effectively makes this InfoPath customization approach [at least for me] unmanageable and unworkable for sustainable utilization in InfoPath Forms Services context. Therefore my design decision to implement the required behavior 'outside' InfoPath Forms Services, via a clientscript approach.