Biden let the Philippines purchase them last year so the precedent exists for Trump to do the same with regard to Indonesia and eventually other Asia-Pacific states too, which could raise the chances of reaching a grand deal with Russia if paired with energy- and Ukrainian-related incentives.
Indonesia's weapon purchases are scattered all over the world. If Americans ban the purchase of BrahMos, Indonesia can stop buying US airplanes (already equipped with more Su-27 and MIG-29 than F-16). For US benefits, more nations in Southeast Asia should own BrahMos or similar high-supersonic anti-ship missiles. Of course, if the USA had something similar for sale, I am sure Indonesia will consider that as well.
What you describe doesn't sound like a relationship between sovereign allies but a hegemon and vassal.
I think it would be a very bad idea to try to block this deal......As soon as US recognize its limitations it will be better for all
Indonesia's weapon purchases are scattered all over the world. If Americans ban the purchase of BrahMos, Indonesia can stop buying US airplanes (already equipped with more Su-27 and MIG-29 than F-16). For US benefits, more nations in Southeast Asia should own BrahMos or similar high-supersonic anti-ship missiles. Of course, if the USA had something similar for sale, I am sure Indonesia will consider that as well.