<nitpicking>
If we're depending on ImageResizer.ResizerSection anyway, it's probably better to just call Config.Current.getConfigXml().queryFirst("presets") so we don't miss elements with case variations. ImageResizer has case-insensitive configuration, unlike the .NET XML library. Copy/paste from https://github.com/imazen/resizer/blob/master/Core/Plugins/Basic/Presets.cs if you want.
</nitpicking> 

ImageResizer also supports the semicolon syntax, not just querystring, so using `new Instructions() ` to parse will enable that. Instructions.Width will return either 'width' and 'w', but not 'maxwidth'. `instructions.Get<int>("maxwidth")` lets you access that.