Sorry, there are no plans for this, but I'm sure with little programing you can convert the data from one grid to pivot table. If you use server side data I recommend you to do this server side using a standart SQL – there are a quite good lessions for this. (you need just to google it)
The onInitializeForm should not be called within jqGrid parameters, but in the parameters of the particular action (search, edit, add, delete) in the navGrid method – See docs.
The search uses the jquery load – you can use ajaxStart and ajaxStop when (maybe you can use here a blockUI plugin) calling the search – and notify the user when the ajax is ended.
Yes you have right – this is one of the reasons that I have moved to UI Theme roller and changed tottaly the concept of the grid in 3.5. In 3.5 you will not have such problems – moreover if you set 900px width it is 900px regradeless of the column width.
