As mentioned by the above experts, the situation might necessitate the requirement of having a PAN.
But, having a PAN will have some consequences like compliances and possible tax effect on income. Since currently the income must be accruing to 19 members individually who might not be paying tax or could be under lower tax bracket, but once we create a legal entity, it might attract tax provision and perhaps the tax at higher rate of say, 30% because the aggregate income of 19 members, which would now accrue to the new entity would be more than what was earlier being accrued to the individual members. Further, the newly incorporated entity will also have to file the tax return....-Cost of compliance with laws.
[There might not be double taxation like it might not happen that the same income is taxed in the hands of the new entity and the old members.]
If the income of ALL the members is in 30% tax bracket, then it might not be much of a problem, but then I suppose those people wouldn't be making "small investment" in saving bank account.
You will need to evaluate as to whether creating a legal entity is going to benefit the individual members?
I am considering this point specifically because there was the reference of "small savings". Small savings is usually not done by very rich people. If without creating a new entity, individual members are not paying tax or are paying low tax then we must think about the benefits of creating the new entity.
Creating a new entity is advisable if the operations are on a big scale, for a small level of operations the compliance burden can hinder the objectives.
[Note-: I have not advised to not to obtain PAN or creating a new entity, whether by way of partnership or Association of persons or any other mode. My advice is to first evaluate the effect of the same.]