This leads to the button to become disabled when the page is rendered but with subsequent additions it does not become clickable.

diable-remove-button

ve.ui.MWTransclusionDialog.prototype.getPageFromPart = function ( part ) {
	var page = ve.ui.MWTransclusionDialog.super.prototype.getPageFromPart.call( this, part );
	if ( !page && part instanceof ve.dm.MWTransclusionContentModel ) {
		return new ve.ui.MWTransclusionContentPage( part, part.getId(), { $: this.$ } );
	}
	var parts = this.transclusionModel.getParts();
	if(parts.length === 1 && part instanceof ve.dm.MWTemplatePlaceholderModel)
	{
		page.removeButton.setDisabled( true );
	}
	return page;
};