^^ It is not that easy to have stuff of our own on anything American made. This includes C-130s and C-17s. To modify anything that is American made with local stuff means that Americans don't get the profit nor the political edge; this is something they don't even allow Israelis and British. Therefore, in general terms, anyone having anything American has to take permission from US companies and their government to modify it domestically. Which means that even if we're going to have our own communication system in this, we will have to ask Obummer and Co. for their official permission.
While LM and Boeing are all too pleased to give anything away, US government has some serious issues about this since any such modification's news out that they've said yes without political clout would mean a final nail in their own product's coffin. For example, if US easily agrees to our own communication systems fitted on C-130Js, it means that in future a country like Indonesia can simply buy the basic C-130 from US without its version of expensive Com system which might be 10 times costlier than what we Indians make, and simply order from India what we made. That way US companies lose money and at the same time, the political muscle to arm-twist a client nation further diminishes.
Knowing that US is desperately trying to keep its significance up in presence of other countries these days, getting Pentagon to agree to our demands on fitting our domestic systems would be tricky from where I see this.