Honestly having a bunch of observing radars with incredibly huge radius right from the beginning is incredibly op...
Make them more balanced / expensive, or at least add a setting to disable them please.

then make a suggestion
- what they should cost for each level,
- which technologies should be needed, with what costs for each level
in such a way that everyone is satisfied ;-)

Well
Stock radar is a 7 radar with scanning too
3 and 5 radars are worse then stock one so keep them as is
9 is a bit better, so I'm add something like engine units (or red circuits) to recipe to balance
Most of the other should be locked behind mil tech and more advanced components
17's area is HUGE already so it should require blue circuits and lds at very least
33 should require other planet tech like fulgora's superconductors
And 65 one should be end game requiring tungsten and quantum processors

Also make their power consumption more aggressive so you'd want an actual reactor for the last one for example

a few thoughts on your ideas
power consumption is already quadratic to the radius which is exact the real progression.
you can build a 33 with 4x 17 or 16x 9 w/o new nechnology, it only saves work during placement.

but i will take it into account when i incorporate difficult grades.

Also make them BIGGER, like the last tier should be like rocket silo in size!

“ like rocket silo in size!” this gets pixelated because I can only scale up the ‘normal’ radar.

• Add progressive sizes for Observer radar (configurable)

is only a part, but everything piece by piece

Take a note that you can make some other changes and not just scale it up
Like take note at https://mods.factorio.com/mod/nav-beacon
It basically combined parts of beacon and parts of radar for a new look