Ah yes, the classic "user-friendly" legacy code. When clients say they want to keep their ancient framework because it's "user-friendly," what they really mean is "this knife will kill you slowly instead of quickly." After 15 years in this industry, I've learned that "user-friendly" is code for "we've already memorized all the horrible workarounds." The only thing friendly about that framework is that it consistently lets you know it wants to stab you in the back.
Pro tip: When a client insists on keeping something this dangerous, just quadruple your hourly rate. Either you'll get rich or they'll suddenly discover the magic of modern frameworks.