So I made a concept for Izsha that I think might fit what you would want.
The problem with the pure structure hero, one that can only interact with structures, is that as the game progresses, you have less and less of an impact of the gamestate. This is particularly problematic in HotS, where you need a presence in objective fights to win. A character that deviates from that gameplay so drastically can cause large amounts of problems and frustrations for players.
What I tried to accomplish with my Izsha was to give her a more universal presence by making her own mobile structures, based on the crawlers from Starcraft. Her ability to fortify and repair her structures is just one way she can influence the game. Her mobile crawlers give her a omni-present impact on the game, able to protect objectives.
If you are interested in my take on a macro structure hero, the link is here: [HC] Izsha, Advisor of the Swarm - #5 by Trixter-11446