I think the Lando forms should stay where they are. Yes Lando-Ts usage exploded due to it beeing very useful in the current meta as it checks a bunch of dangerous things. But lets be realistic here, its not like its all that dangerous. The Scarf set is incredibly prediction reliant because beeing locked into EQ, Superpower or Stone Edge is very undesirable so every time you use it to check something you have to predict if the sweeper switches or stays in. If you go for the kill you might end up giving something a free switch, if you go for Uturn predicting a switch you might get your ass swept. The Pivot set is useful no doubt, but here again its hardly threatening at all. Without investment 145 base atk isnt that impressive and your coverage is limited since U-turn and SR are basicly a must have on it. Then we have the lack of recovery meaning it cant switch into the things it wants to check all that often. And bringing up usage as an argument... We should all know by now that usage and viability are two different things. Imo Lando-T is just a useful glue to many teams because its a halfway decent answer to many threats while also providing SR. Regarding SR however it should be mentioned that its not realy a good setter as most hazard removers beat it. At the end of the day it does a lot of things but none of it realy well. It can check stuff, but gets worn down fast, it can set SR but sucks against most defogers/spinners, it can revengekill with a scarf but doesnt want to be choice locked at all cause its moves are so easily exploitable. Yeah its easy to slap on a team but still, imo its no S rank material even with lowered standards.
Lando-I however is a huge pain in the ass unless your running one of its few counters. Switching into it is painful as hell and there isnt much that can do it without beeing heavily crippled. It can set up SR as well and is arguably even better at it as it can beat some of the hazard removers. Its far more versatile than its therian form which is limited to 2 sets who always run the same moves with very little room for changes and the few changes it can do dont realy affect the things it can handle. Lando-I on the other hand can change its role, and its counters so drastically that you dont want to deal with it at all until you know the full set. CM, RP, Sludgewave, Knock off, Focus blast, Psychic, SR yes it cant use all of it which is kinda problematic for the user but never knowing which move it has is still very problematic for the opponent. Slapping it onto a team is just as easy as its therian form because every team loves the power and utility it brings and since it doesnt need any support it can fit into every kind of team. Unlike the T form its incredibly strong against defensive teams while still beeing usefull against offensive ones. Yes there is a bunch of faster stuff that can force it out but getting that stuff in is a pain and lando has no trouble what so ever just switching out and come back in later in the game to be a pain again.
to cut a long story short:
Lando-t:
excellent glue to many teams, better against offensive teams, can perform 2 roles but isnt all that good at both of them, useless against defensive ones
Lando-I: Useful against offense and defense, incredibly hard to switch into, unpredictable as it can perform many different roles well.
And yeah i see it more from the "how threatening is the mon" than from the "how easy is it to slap it on a team" point of view because its the first group that i have to consider when i build teams and that give me a headache ingame when i have no way to deal to with them. If your unprepared for Lando-T its not gonna hurt you all that much cause its easy to play around, wear down and to check/counter, beeing unprepared for Lando-I can fuck up half your team before you can get rid of it.
Oh and regarding Keldeo, please stop acting like it can break through all of its counters because Scald has a 30% burn chance. Often enough you wont get a burn in the first place and even if you do things like Recover Lati@s, Venu, Slowbro, Amoon, Cune etc still wall you to hell and back for all eternity even if they are burned. Sure they dont like it but their ability to do their job isnt hampered all that much. Chances are high that Keldeo wont do much if anything at all when there is one of those mons on the opposing team.