I would tell the owner that the preferred course is to strip this. The decision hinges on factors ranging from aesthetic to financial. Besides that, too may layers of paint promote cracking. On the other hand, if you're talking about a side of a building that people usually don't see, the customer might junk aesthetic considerations and keep surface prep to a minimum. For that matter, the customer may not be able to afford total stripping.
Some paint films cry out to be removed.
For Dufort, if 50 percent of the paint is cracked and peeling, he prefers to strip off everything. If diamonds around the X come off, you've got a problem with adhesion and you'll need to take that layer off. Whether you strip it all off or just the loose stuff, you've got quite a selection of tools to choose from. Although it requires great skill and caution, torching old paint is Dufort's preferred method, due to its speed and efficiency. He uses sanders as a follow-up to smooth out imperfections and feather paint edges.