Hey Mark,
this morning I hard coded the brushes in your code and they all work great (including Smooth and Masking brushes).
Also no Warning is displayed for Smooth and Masking brushes when running the script (the thing you were worried about).
So at the end of the day you created a great script ! Many thanks again. 
Here follows the script code I created (with my ownd harcoded brushes) using your code: maybe someone else may find it useful. 
Apologies for the flat highlighting but I cannot get a decent colorcoding in Notepad++. 
I also attached the .txt file so to preserve the correct code indentation (as you did before).
[IConfig,4.73]
[ISubPalette, “Zplugin:Brush WrapMode”]
[VarSet, brushCount, 34]
// brushes() defines the pathname and brushType() defines what type of brush it is.
// 0: standard modeling brush.
// 1: smooth brush.
// 2: masking brush.
[VarDef, brushes(brushCount), “”] [VarDef, brushType(brushCount), 0]
[VarSet, brushes(0), “Brush:Morph”] [VarSet, brushType(0), 0]
[VarSet, brushes(1), “Brush:Standard”] [VarSet, brushType(1), 0]
[VarSet, brushes(2), “Brush:Dam_Standard”] [VarSet, brushType(2), 0]
[VarSet, brushes(3), “Brush:hPolish”] [VarSet, brushType(3), 0]
[VarSet, brushes(4), “Brush:Flatten”] [VarSet, brushType(4), 0]
[VarSet, brushes(5), “Brush:Planar”] [VarSet, brushType(5), 0]
[VarSet, brushes(6), “Brush:TrimDynamic”] [VarSet, brushType(6), 0]
[VarSet, brushes(7), “Brush:TrimAdaptive”] [VarSet, brushType(7), 0]
[VarSet, brushes(8), “Brush:TrimSmoothBorder”] [VarSet, brushType(8), 0]
[VarSet, brushes(9), “Brush:MalletFast”] [VarSet, brushType(9), 0]
[VarSet, brushes(10), “Brush:MalletFast2”] [VarSet, brushType(10), 0]
[VarSet, brushes(11), “Brush:Move”] [VarSet, brushType(11), 0]
[VarSet, brushes(12), “Brush:Move Elastic”] [VarSet, brushType(12), 0]
[VarSet, brushes(13), “Brush:Alpha”] [VarSet, brushType(13), 0]
[VarSet, brushes(14), “Brush:Clay”] [VarSet, brushType(14), 0]
[VarSet, brushes(15), “Brush:ClayBuildup”] [VarSet, brushType(15), 0]
[VarSet, brushes(16), “Brush:ClayTubes”] [VarSet, brushType(16), 0]
[VarSet, brushes(17), “Brush:ClayPolish”] [VarSet, brushType(17), 0]
[VarSet, brushes(18), “Brush:ajClay”] [VarSet, brushType(18), 0]
[VarSet, brushes(19), “Brush:ajPolish”] [VarSet, brushType(19 ), 0]
[VarSet, brushes(20), “Brush:ajNoise”] [VarSet, brushType(20), 0]
[VarSet, brushes(21), “Brush:Orb.Cracks”] [VarSet, brushType(21), 0]
[VarSet, brushes(22), “Brush:ajCracks”] [VarSet, brushType(22), 0]
[VarSet, brushes(23), “Brush:ajPinch”] [VarSet, brushType(23), 0]
[VarSet, brushes(24), “Brush:Pinch”] [VarSet, brushType(24), 0]
[VarSet, brushes(25), “Brush:Inflat”] [VarSet, brushType(25), 0]
[VarSet, brushes(26), “Brush:Magnify”] [VarSet, brushType(26), 0]
[VarSet, brushes(27), “Brush:CurveTubeSnap”] [VarSet, brushType(27), 0]
[VarSet, brushes(28), “Brush:CurveLineTube”] [VarSet, brushType(28), 0]
[VarSet, brushes(29), “Brush:Smooth”] [VarSet, brushType(29), 1]
[VarSet, brushes(30), “Brush:SmoothValleys”] [VarSet, brushType(30), 1]
[VarSet, brushes(31), “Brush:SmoothPeaks”] [VarSet, brushType(31), 1]
[VarSet, brushes(32), “Brush:MaskPen”] [VarSet, brushType(32), 2]
[VarSet, brushes(33), “Brush:LazyMask”] [VarSet, brushType(33), 2]
[IButton, “ZPlugin:brush WrapMode:WrapMode Main Brushes”, “Toggle WrapMode of the Main Brushes between 0 an 1.”,
[IFreeze, // Stops interface updates while we switch brushes.
// Store the currently selected modeling brush.
[VarSet, currentBrush, [IGet, 30516]] // 30516 is the Brush slider.
// Determine the new WrapMode
[If, [IGet, “Brush:Curve:WrapMode”], // WrapMode is 1 or higher.
[VarSet, newWrapMode, 0]
,
[VarSet, newWrapMode, 1]
]
// Set the new WrapMode for the currently selected brush.
[ISet, “Brush:Curve:WrapMode”, newWrapMode]
// Store the currently selected smooth brush.
[IKeyPress, SHIFT,
[Delay, 0.05] // Apparently needed to read the brushName.
[VarSet, brushName, [IGetTitle, 30516]]
[VarSet, smoothPath, [StrMerge, “Brush:”, brushName]]
// Remove the . and space from the path.
[VarSet, smoothPath, [StrExtract, smoothPath, 0, [StrLength, smoothPath] - 2]]
[ISet, “Brush:Curve:WrapMode”, newWrapMode]
]
// Store the currenlty selected masking brush.
[IKeyPress, CTRL,
[Delay, 0.05] // Apparently needed to read the brushName.
[VarSet, brushName, [IGetTitle, 30516]]
[VarSet, maskPath, [StrMerge, “Brush:”, brushName]]
// Remove the . and space from the path.
[VarSet, maskPath, [StrExtract, maskPath, 0, [StrLength, maskPath] - 2]]
[ISet, “Brush:Curve:WrapMode”, newWrapMode]
]
// Then set WrapMode for the hardcoded brushes.
[Loop, brushCount,
// Checks if the interface path name or UI ID exists.
[If, [IExists, brushes(index)],
[If, brushType(index) == 0,
[IPress, brushes(index)]
[ISet, “Brush:Curve:WrapMode”, newWrapMode]
[LoopContinue] // No need to check for other brushType().
]
[If, brushType(index) == 1,
[IKeyPress, SHIFT,
[IPress, brushes(index)]
[ISet, “Brush:Curve:WrapMode”, newWrapMode]
]
[LoopContinue] // No need to check for other brushType().
]
[If, brushType(index) == 2,
[IKeyPress, CTRL,
[IPress, brushes(index)]
[ISet, “Brush:Curve:WrapMode”, newWrapMode]
]
]
]
, index]
// Restore the previously selected smooth, mask and modeling brushes.
[IKeyPress, SHIFT,
[IPress, smoothPath]
]
[IKeyPress, CTRL,
[IPress, maskPath]
]
[ISet, 30516, currentBrush]
] // End of IFreeze
, /DISABLED ?/, /BUTTON WIDTH/, , /BUTTON ICON/, /BUTTON HEIGHT/]
