Will there ever be a new tier level of research added to the game?

Unlikely

Have been playing for 3 years now and its still an addictive game, but it would be nice to see some advancement put int to the games basics instead of just top end candy

best we can hope for is more CT lab discovery and they take millions (and luck, so much luck). While all the reserches do need upgrades (except maybe relays), as both npc drops, badage drops and mission drops ALL outstrip the very best our minds can offer, apparently our scientist community is content to suck high upkeep cost ineffective moduals as the new standard.

Things that would be nice

A mod for each type that adds a % modifier. (Attack, Defense, Hull, Sheild, Energy)
a 1:1 standard building (we have loads of 1:1 or better artifacts this should NOT be something new to our scientists)
a 1:1000 population building (we have quite afew artifacts that do this or FAR FAR better)
a soild % + good bonus cloak/defense/offense building. (again load of badage/mission artys do this why can we not derive something from the stuff we have scavanged?)

Preferably these would have EM, XTS9 and/or political favor costs.

1:1 tbh is kind of just a waste of time because theres enough 1:1 already and I wouldnt bother to research it. Since its last tier, it has to be RP intensive, or else why bother adding it. So I propose it should be 2:1. But a smaller size building. Maybe size 2, +4 AP? Sounds pretty balanced in power vs overall size for an endgame thing.

1:1000 pop -> Pop honestly doesnt really matter anymore in this game, and like you said, theres already enough mods to replace this that are extractable and easily accessible that this shouldnt be needed.

a +% research cloak mod would be overpowered. Its already ridiculously easy to cloak planets up beyond max scan due to all the things LMs give and with the addition of Polaron Emitters. Why make your scan runs even worse? If your doing a project, it should be unscannable anyways and production doesnt matter until its finished. Polaron and 1 of ergo/MTJ/CSR/Xathe inhib/Repulsor (see how many choices there are?) is already good enough when its incomplete. And youll probably have a random +5% on your project anyways like Tejiar HQ or Ryelis Analyzer. By the time the AP mods are all in place, you should have maxed cloak to 3.9k already, and picked up another 1-2 +% cloak mods to slap on.

you make some fair points what about some mods that make it harder to invade, ie decrease the cap on invade % say by 2 or 3% each? so have 10 the max invade chance is 60% ect.