Thanks for the reply. I have following to submit.
Selecting one font for complex text and latin text and making both texts readable at a time is possible if that one font has both complex and latin support. But, all those fonts are not necessarily good for publishing work. Those which are good for publishing the complex text matter may not have support for latin text. Moreover, the size, style etc for complex and latin can not be changed individually. We have to accept the size etc which the font forces upon the user. If we look at the Libre Office's character formatting window, its very clear that a Paragraph style provides options to set different fonts, size, style etc for the latin text and complex text. The screen shots of Libre Office are attached below.