in ext 4.02 no... i dont konw if exsist 4.03 or later! And about your question to "hook" the answer is: not possible. Spring and Struts work only via html tag standard, so in the past via extjs3 i transfom them with look and feel better.
Unfortunately, from a server-side perspective, we're in unfamiliar territory for me, so I don't know what to recommend, short of the horrible solution of writing your own transformation code to rip out the controls and their values client side and recreate them in place.
Sencha really seem to have made a design decision to deprecate (or partially eliminate) support for legacy HTML apps!