Not a good logic but just thought with in 1 min(may be its a foolish thought).
Make one loading iview. when it displays call RFC's by raising some event and move to next iview.
So till RFC execute, it will show first iview.
breake those information into dc's....and then make a dc which would contain the application with whole structure..that you can develop my giving tabs into the wd application....create dummy iview's for each tab which would actually call the correspoding dc's using the help of controller...you can write a whole different controller for this....this way, when you run the application, only the dummy iviews would be loaded and by clicking on the tabs only the actual iview would be loaded by calling corresponding dc's...give a try this...this would take some time as it's a whole architecture structure change....but you have time, so go ahead 
cheers,
sen
Thanks all
We decide to improve the code and now is faster.
Also i think the best is creating a loading view and use a time trigger to call RFC.
