I am unclear on what the pavers are for. Are they a patio or are you using them to create the fire pit? I think that in this case, building a patio that is dry laid and has pavers over the top of the sump hatch but can be just lifted off when access is needed would be fine. Then get a freestanding structure to hold the fire such as a chiminea or a metal dish fire pit would work. Or if you want something more permanent as the fire pit, build it on one side of the patio.

if you are considering using the pavers to build up sides and using the hatch lid as the base, I would consider that a poor idea. Too easy for uneven temperatures to crack or otherwise damage the lid.

You are going to need to put a proper base layer under the pavers so they stay stable since you are in a cold area. Why not make it somewhat thicker so the pavers cover the hatch and then you can put the fire pit wherever you want it rather than having it dictate the fire pit location? Or is the hatch in your ideal fire pit location already? With a well-prepared base, the patio can be in any configuration that covers the area, and the fire pit also has flexibility of location. Or if that isn't the best location for the patio, make it something else such as a garden bed with a realistic fake rock over the hatch and locate the fire pit and patio in the ideal area. I guess I am asking if that is truly the best spot for the fire pit and patio since I have no way of determining that from the photo. If it isn't, find a different solution for the hatch.

As long as it is dry laid (no mortar, just sand swept between the blocks) covering the cover withhe patio bock shouldn't be any issue since you would lift out the ones you need and then replace after the access has been completed.