This is merely a thought process that is gaining traction at present times. Till as such time a firm agreement is entered into (here, Mr Biden's administration's posturing and actions will be the determinant), one can always expect a last minute flip flop.
Rationale is simple.
India simply can not (in the opinion of the policy makers and decision makers) afford to buy the amount of aircrafts that they need to offset the technological gap that is now emerging with its principal adversaries to the north and to the west. Also, there remain a lot of issues with the LCA which was always a Project (been saying this forever) and its indigenisation fraction as claimed by DPSUs must be taken with a solid kilo of salt, principally, the engine remains an elusive entity.
These two factors coupled to the signing of multiple bilateral agreements with US, have driven in a realization that the Project LCA needs an engine till as such time the tech stabilizes and matures (another 3-4 decades?) and going with US option allows for the availability of the GE F404 and GE F414 engines to be supplied as also the access to number of platforms from US' stocks that can be made available in case of requirement in an actual war. Also, leasing allows for India to actually gain access to technologically better platforms at relatively affordable rates. In the meanwhile, the Project LCA will progress with LCA Mk1a hopefully being inducted in numbers to atleast retire the Mig-21s.
I feel there is too much contradiction in this post. If our policy makers have decided that we can't bridge the technological gap with numbers, then the answer is to either not fight or bridge the gap using more sophisticated technology with lesser numbers.
If the rationale is we need Super Hornets in less numbers now so that the numbers can be bolstered during war through EDA transfers from the US, then 2 problems come up. One, the SHs will not be able to fight such a sophisticated adversary anyway. So all we will end up doing is creating more PLAAF aces without achieving anything. You can be sure the SH is not going to penetrate PLAAF air defences in the near future.
The second is that it takes 2 years to train a pilot to the point where he can fly the SH on his own. Different story how long it's going to take such a pilot to actually use the SH to its fullest capability. And only you can tell us what are the chances of survival of a downed pilot from plains on the plateau. So unless we plan on fighting the Chinese for many years, fighter jet transfers from the US is going to be largely useless. This can only work when it comes to support aircraft with trained personnel available in numbers and other types of combat systems where the training time is easy and quick.
Anyway this idea about leasing and transferring jets from US actually works better with France. Don't get fooled by the number of jets that the US operates. According to the USN, they are currently short by 40 jets. And the F-35C doesn't meet the requirements necessary to replace the SH by role. It's going to take at least until 2035 before the NGADs are in enough numbers that the USN will be willing to part with their SH, which will be far too old and meaningless by that time. Otoh, the French are sitting with 50 surplus Rafales today and that number will increase to 100 by 2030. Half their fleet is kept in storage. Also, converting and training a pilot to fly the Rafale is much quicker. There's also the question of survival of the SH's production line. Boeing is hoping Finland and India will keep their line open beyond 2025.
Due to the sophistication necessary to fight the PLAAF, along with the fact that we need an air force to have a surplus amount of jets for EDA transfers and a running production line, this argument only works in favour of the F-35A when considering all American jets.
I wouldn't worry about the LCA or the support needed from the Americans to make it happen. If the MoD becomes serious about it, the LCA's American engine can be replaced with the K9+ within just a few years, it needs only 2 more years of development time, including flight testing. And I wouldn't worry about the import content as well, people have unrealistic expectations from just 20 FOC jets. You can't tell an Indian company they will only be manufacturing their component for 20 jets, they won't participate. And ADA/HAL are buying foreign components in batches, so each successive batch is going to be more indigenous than the previous, which is why there's talk of replacing the Israeli radar and EW suite with Indian in the final batch of the 83 Mk1As.
As for the LCA Mk2, again, let's see where our contract with France goes. If the engine deal goes through, the K10 will need 5-10 years to become available. So the engine can be used on later batches of the Mk2, and also during the MLU of the first few batches.
Anyway the entire LCA family uses different engines compared to the SH, they are not transferrable. All three jets use engines of different dimensions and different materials. Also, as long as we are still in the good graces of America, we do not need to import their fighter jets just to keep our engine deal going. We only require political will to make the indigenous LCA engines happen, the technology already exists, and the Americans will work really hard to scuttle that if more than half our air force ends up being dependent on American engines. You can then be sure that the 30-40 years you have given for an indigneous engine will come true.
Lastly, about the affordability of the MRFA, that argument is completely misplaced. By the time the MRFA deal is signed and the first squadron is inducted, it's going to be 2028 or 2029. Even if we take a pessimistic view of the Indian economy of that time, the IAF's capital budget will still be at least two to three times greater than the cost of even a full MRFA squadron a year, let alone the planned 12 per jet.
You spoke about ordering 64 SHs for the IAF, but the IAF will see much greater benefit if a follow-on order for 36 more Rafales are placed, the capability provided will be greater and it will come at a much cheaper rate. And a more prudent approach would be to complete the K9+ and K10 with French assistance, they have promised full ToT and IP transfer, so that at least later batches of the LCA Mk1A and Mk2 can be equipped with them thereby reducing forex outgo to the US, who have already decided that they won't be transferring engine tech to India.
Finally, if the PLAAF is going to be far too sophisticated, I think the IAF are the only ones who can make the best decision possible on how to counter that. And with their open support for the MRFA, and claiming only AMCA will be their next gen procurement, it appears they have already made a decision on fighter jets for the next 15 years.