Sir, The point you mention are correct and true in their scene, But issue here is lack of spare not only imported, Following points below >>
1. Lower number is deciding factor of duration assemblies lines running for spares which are pre order from Pvt industry, Pvt industries also have their own production facilities which manufacture such low quantity for short order and then remain idle even when their is requirement..
2. The pre calculation of spare for a tank / Arty / Vehicle life cycle in India is always messed up, Let it be other tanks of IA also, 900 T-72M1 remain junked as they don`t have spares, T-72M1 are made in India completely afaik , This is something noticeable and common around..
3. My bad Sir, I was using layman`s language to say base workshops are field workshops, Lack of overhauling facilities of Arjun is a major reason for lack of spares as it is a lot more expensive to design and made a tank than to make overhaul facilities all over the country, This factor is mostly overlooked and the factor is very serious..