What type of on-boarding system/process must be in place in order to keep the energies of the employees focused towards maximum performance?

A good induction is necessary for a new employee.
There can be a coach nominated for each new employee in his/her location.
On top of that, the general HR stuff can be introduced by HR representative from the hq on a call + in advance sent presentation.
There are so many ways to start the journey well for a new employee.

Onboarding / Induction is a critical process in the New Joinee's Lifespan in an Organization.
The more pleasant and honest the indution process, the better are the chances of the New Employee performing at his/her best.
Many companies in India have presence across multiple locations and have an HR Spoc who meets and greets New employees as a part of the On Boarding Process.
An email is sent out introducing the New Employee with a few details about his/her professional background.
A coach or a mentor must be assigned to help the employee settle in.

An effective onboarding process helps with the smooth incorporation of new employees into the work culture and keeps employees engaged as well.
Considering the scenario given since your HR resources are primarily based at the HQ, it would help to assign mentors/ resources in all locations.
It would be nice to prepare the new joiner before s/he joins the organization with the expected schedule for the first day/week/ month and explain the onboarding process as well.
Ensure that all relevant documentation (New joiner documents, Orientation about the company, policies and procedures, training material, etc.) is made available online which can be easily accessed by new as well as existing employees.
Also set up internal tech systems that help you reach out to employees in all locations and inexpensively have frequent conversations with them.

To answer in a single word: Virtualize Leverage technology to the maximum - in today's world you do not need to have a physical presence everywhere.
Taking your points of a fast paced organization / number of HR team / budgets.
All your team at the HQ should contribute a %age of their time towards handling calls from potential candidates - a phone number which would be shared with the candidate : So at any time the candidate has a question he/she can reach out and speak to a REAL Person.
A kind of a Quasi-Shared Service Center.
In addition to the above - create a virtual on-boarding program and on a specifc day of each month you can have a virtual induction via web-ex where the HR as well as the concerned stakeholders address the new employees.
I can go into a lot more detail but for want of time/space and in interest of brevity - will leave you with these thoughts.

Our on-boarding and orientation is divided into two parts, first, on joining day, individual is welcome by HR reps and we handover the appointment letter, ID card and details of company profile/operations back by some important pointers and this has been explain to them in detail via presentation and side by side address their queries too. This session last for few hours and then individual is placed to head of department who greet him and then guide him toward his work station and introduce him to team. The1st day we do offer them lunch and other complementary give away and it’s like a bit soft introduction of company. In second phase, if employee need to have detail orientation of the company or associate department then we(HR) chalked out a detail orientation plan with stipulated time and duration with support from all department and section  heads. I did work on designing various details orientation plan of Plant engineering, production, finance, logistics and QMS division which flow wise working. I keenly focus on various steps, documents and formats with introduction of key individual with our locations and division and keep them inform earlier so that if any changes are required then we do update all. I believe a detail and well-designed orientation plan always help a new employee to have quick grasp on work and help in their learning.

as per customer requirement and his attitude

First and foremost is intensity of training and orientation for the newly hired team members. The on-board orientation on top of the regular training and organizational orientation should include values sharing and formation. In this manner, the organization can be confident that when the people are deployed to their respective areas of assignment, they are also aware of the company's sensitivities. This awareness of the group's sensitivities will drive the employees natural instinct to compete, excel and survive.

 

In addition, maximized use of the present information technology available  can be used by management to keep visibility and follow-thru.

motivate them as much as you can so, it give them more power and energy to work.

motivation can be through bones , salary increase , freindly team and a confirtable working hours.