Following Mazhab Islamic Jurisprudence Need mechanism Rationality

Need of well established jurisprudence
Life is in motion Time is always moving ,and the world will have new situation and challenges till the day of judgement.. Changes brought about by time and spaces are destined to come and Islamic ruling have to solve these needs of humanity according to Quran and Sunnah.. New situation can come on so many fronts. The Administration of a country with crores of population, legal status of Share markets and details of Islamic finance, Status of Muslim in a country where majority is non believer, use of mobile, and newer communication system, and countless other situation of local and of universal nature.
Take a real life example ...............
 With the advent of ULTRASOUND we can know the status of developing fetus and if it is found fetus is not developing and fetal heart sound has not come they will do MTP or Medical Termination of Pregnancy...............Now what will be ruling for those women about purity and offering Salah. The blood coming after MTP will be Nifas blood/simple bleeding............. Now you have two option either apply your mind with your limited knowledge of Quran and hadith or consult a person who has the requisite competence.  So naturally there should be a permanent mechanism to deal the situation. (example from jaded fiqhi masail…………..taqi usmani………..fiqh folder.
So this is arrangement from Allah so that can withstand all the Thats why a full department is developing as JADEED MASAIL AND ISLAMIC PERSPECTIVE FOR THEM,Maulana Taqi Usmani,and Maulana yusuf ludhianwi from pakistan and Maulana khalid saifullah Rahmani from India are remarkable name working in this field.
A permanent mechanism should be for derivation of rule from quran and sunnah
The above discussion emphasize that there should be permanent mechanism to withstand all the changes brought about by time and space and can solve all the time bound needs of humanity till the day of judgement. dealing the  solution to there are Islam has solution of all challenges
Is it a handicap situation of dependency on IMAM/JURIST????
If you look superficially it seems there is dependency on Imam/Scholar for deriving Islamic law and it is a handicap situatin but actually it is a divine arrangement. Islam is final massage and it deals with all aspect of life till the day of judgement. So this is arrangement from Allah so that Islamiic priciples and ruling  can withstand all the changes brought about by time and space and can solve all the time bound needs of humanity till the day of judgement.
The great scholar of Islamic history, reformist and king Faisal Award winner Maulana Abul Hasan Ali Nadvi ( Ali Miyan) R.A. describe this situation of second hundred hijri in these words in his book Tareekh e dawat o Azeemat vol 1(page 80-81) {its English translation The saviors of Islamic sprit.”}
“Islam has expanded  to a vast and fertile areas of Syria, Iraq, Egypt and other African countries,Iran and central Asia. Administration of country, Maashrat, business, has reached to a complex situation. And it was urgent need to extraction and ISTANBAT and interpretation of the fine details of these principles. For this important job a very deep knowledge and understanding of Quran and sunnat and its practical application to the current situation were required.”
Need for permanent mechanism and its realization by Salfus Salihin
The Ulema and Mashaikh realized the situation in time and hundreds of scholar started devouting themselves for this noble cause. They took it as a permanent job. They were not only the famous four Imam but so many others either working at different Islamic centers.May Allah give them best reward.
Ali Miyan  further writes in his book
“It was bounty from Allah and pinnacle of destiny (IQBAL MANDI) of ummate muslima that muslims got people of special qualities for this important job.
They were outstanding in knowledge of quran and sunnat, intellectuality, piousness, piety,and Ikhlas. Thousands and thousand of such person devouted their life for this noble and essenitial cause. There were more scholar group but out of these four distinguished Imam emerged whose Jurisprudence ruling were compiled in a systematic way and their ruling is still alive and popular. These are Imam abu hanifa (Died 150 hijri,followed by nearly 47 % of muslims). Imam shafai (Died 204 H followed by 16 %) Imam malik (Died 179 H followed by 29 %),Imam Hanbal (Died 241H,followed by 2 %) . They comprise nearly 96 % of the total muslim population of the world.
            These Imams got very competent and  uncomparable quality disciple.Imam Abu Haneefa got Imam Abu yusuf,and Imam Muhammad,Imam Malik got Abdullah ibne wahab,ibnil qasim,Imam shafai got Muzni and Rabi, and Imam Ahmad got Person like Ibne Qadama.
Benefit of this system 
They not only derived ruling but also compiled the basis of ruling from quran and sunnat, Deviced principles that helped further generation of ulema and scholar to derive rules from Quran and sunnat and to guide muslims on all aspect of life, including finance and administration etc.