the reason why MCA is not that ambitious is that it shares a lot of technology with the LCA.for example it uses the same engine(though uprated),wing sections ang other subsystems.in aerospace industry it is not uncommon to go for a family of products belonging to different generations,which are basically,development of the same product.eg;su-27 family.another example is from the indian space launchers.india developed SLV-3,ASLV,PSLV andGSLV in a sequence so that systems and sub-systems from one launcher can be used for developing the next generation launcher.in the same way,once LCA is inducted into the airforce,the work on MCA can be started at once.the date of induction of LCA is not that far considering that three LCAs are already flying and has gone supersonic sometime back.yes there has been some trouble with kaveri engine,but that wouldnt stall the programme.i donot know where you got your information on structural cracking,avionics and software glitches though.coming to the time taken for the project,let me ask you how long did the f-22 take to become what it is today?well over 20 years(i donot know if it is in service yet).