I know the tag pool has been done away with because of its many meanings such as billiards or swimming or what have you.

I would like to tag 'pool' to images that are, in a pool. I like to find sequential art on here with multiple pages and it would be a benefit to me to be able to only pull up images that are part of such sets. I can search for 'comic' with decent results, but I get a lot of one-shot pages when I do that, and some sequential pieces are single panels that would not get tagged as 'comic'.

Trying to search the pools themselves is difficulty, in my experience, so just being able to toss something in the post search that'll bring up images that are part of a set would really help me out.

This does not negate the fact that 'pool' is a very ambiguous term and 'sequential_art' is the name of a comic strip.

What do you guys thing would be a good tag to flag this with? I've got nothing.

inpool:true. Read your search options before you ask for something that already exists.

Like I said before you should really put some more effort into learning about the e621 system before suggesting changes. In this case you would have saved time by reading the e621:cheatsheet.