Is he worth being near the top of the list of champs that should get that? Not at all.
Why not?
I need to shed some light on the subject. First off, LoL is the most popular game in the world because of its competitive nature. This means the huge interest for broadcast of pre LCS circuit, thus allowing Riot to create LCS format across the world without much worries for financial turnover. This further means that meta champions are what most public sees (the one not involved in the game already), and what should bring more people to it and make them love it. If it is stale like right now is in top lane (Ekko, Maokai, Poppy) https://www.reddit.com/r/leagueoflegends/comments/4ic38f/at_msi_the_top_lane_matchup_has_been_one_of/
people would not see much diversified gameplay. Not only that, but competitive players, who are already engaged, have little to no fun playing, since they are forced into the limited choice of champions to succeed. I know for my self as a top main, I really don't enjoy that choice, thus so many games Nasus and Dr. Mundo.
With this all being said, each and every champion in the game deserves to bring a competitive side with itself. Nasus is surpassed in each category he could compete, be it split pushing, tankiness or crowd control. If there was a team comp, no matter how small niche, in which Nasus could take part and win a competitive match, I wouldn't find him this unviable.
The whole post is made since there isn't, and I find his E the most useless spell in his kit, although W and R aren't that greater. The only thing that makes Nasus still played is his Q, stacking damage and hope your team doesn't make you leave the lane every minute to teamfight because you lose out on potential. This means that if rework is to be done, the only ability that should stay is his Q, the signature ability. If Riot doesn't want to spend that much resources into reworking (revamping) this champion, changing E, Spirit Fire, should be priority, and wouldn't require for much investment.
Edit1: typos