With a single AutoCAD command you can change rectangles drawn with the command RECTANGLE to true rectangles, which also behave like rectangles.
Compare the following two animations - they illustrate the behaviour of two similar objects. The first one is a normal rectangle created using the standard AutoCAD command. The second one is a true rectangle ("rectangle on steroids" if you want), which also behaves like a rectangle during grip-editing and other AutoCAD editing operations.
So how to get a true rectangle from a standard rectangular polyline (pline)? Just a single "magic" command is enough: AUTOCONSTRAIN. With this command you will add automatic geometric constraints to the selected object - and these constraints will be then kept also during editing.
So you can e.g. add a new command for drawing rectangles to your AutoCAD command set (to the ribbon, toolbars, etc.) - use CUI and the following menu macro:
This new command will directly create the "true" rectangles. Such rectangles will behave like rectangles even in AutoCAD LT 2010 (and higher), which itself cannot create such kind of constrained objects.
You can suppress displaying the constraint bars by setting the CONSTRAINTBARMODE variable to 0.