Well, I will be working on the "Panamax" padframe shortly, which is a 128 pin expanded padframe with lots of extras including dedicated analog pads. It will be used for the next-generation Caravel chip, but there will also be an open frame version of it that would be a good fit for an expanded Tiny Tapeout.

What's the expected bandwidth on Panamax analog pins?

I am not sure. I don't recall seeing any figure for the sky130 analog pad, which is what I am planning on using. Possibly I could go with my "minimum ESD" pad, but that hasn't gone to silicon and so hasn't been characterized. My best guess based on the amount of ESD diode diffusion connected directly to the pad would be about 1GHz for the sky130 analog pad, maybe a bit less, and about 2GHz for the "minimum ESD" pad.

So you are expecting the max signal input might be in 2ghz range (0-2ghz)?

You cannot change the pad type for TinyTapeout, at least not for the immediate future.

Sorry let me clairify that, I was thinking of putting an 'experimental' pad in the space I have for tinytapeout, and non-destructively test capacitive coupling first, then attempt to remove enough of the encapsulation to contact the 'experimental' pad that is not connected to anything else. This would only make sense if someone else thinks it would be a valuable experiment, or I can stick to trying crazy non-galvanic contacts without going outside the tinytapeout space

You don't want the full pad for that with its baggage of way too many power buses. I made a simplified pad which is now in the PDK called

sky130_ef_io__analog_minesd_pad_short

with only the ESD power and ground buses next to the pad. That would be the one you want to use.