I am very much practical but only you are not. arre bhai who will allocate funds to IR or the coach factories to upgrade facilities and manufacture. IR don't have that much resources as it has to simultaneously fund track and station maintenance and construction, construction of the ongoing projects etc. Central govt isn't going to give extra money, most of their money is spent on defence and then on infrastructure, education, healthcare and loan repayments to world bank etc. But fast production of LHB needs many fully automatic manufacturing plants, so huge investment is required. So we need money which we can get only by PPP-model. For PPP a lot of paperwork needs to done which include tender floating, bidding, selection process and then many agreements, clauses etc which takes a lot of time. Then setting up of new plants, extension and upgrade of the existing plants(RCF Rae Bareilly hasn't...
more...

started production of its full scale and ICF Perambur has involved into LHB production very recently). For that a lot of land needs to be acquired which is a big hurdle in all industrial projects in the country. Before construction of the factories, environmental and other clearance has to be obtained. Then there will be obstruction from workers unions which govt organisations always face. To generate revenue, IR will try to further increase fares which will become an indigestible thing for the common man. And with LHBs and its manufacturing there are many technical issues as mentioned in a previous comment by "dsp.hp" sir and so many fuel guzzling EOGs isn't a very economical option.
DON'T get my statement wrong, I am not against LHB. IR will be fully LHBfied and even I want that to happen as soon as possible but it will take time even if fast and correct measures are taken. IR has 62,924+ passenger coaches(which even the Japanese and French don't have) and to fully replace them with LHB coaches, it will take minimum 10 years from now.
GDP and the value of currency will only increase when productive things happen, but to make it happen there are hurdles and "PRACTICALLY" it takes time and RBI(not all banks) can print money as much as it wants.