Now, once all forms in Delphi application are modified to support Large Fonts and System Font ok, there are two forms outside of control. These are the forms that are invoked by InputQuery and MessageDlg VCL functions.
Fortunately, MessageDlg supports Large Fonts and System Font ok. InputQuery supports only Large Fonts, and does not support System Font.

Screenshot: Original InputQuery when System Font is Tahoma

InputQuery implementation is hidden inside VCL, so a patch VCL source code is needed.

1. Locale Dialogs.pas unit in VCL source folder
2. Save As Dialogs.pas to project folder using NewDialogs.pas file name
3. Go to Project/Options window, then go to Directories/Conditionals tab, then go to Aliases/Unit Aliases group and define new unit alias: Dialogs=NewDialogs
4. Locate InputQuery function in implementation part of NewDialogs.pas unit
5. Insert code from previous two posts adjusting Custom DPI and System Font right before "if ShowModal = mrOk then" line
6. Build the project

The resulting InputQuery window will look like: