I'm sure most people see that Tzars and Fatboys are basically only rushed or totally ignored throughout a game because they're just plain not very effective units. Without getting into some unit-specific reasons that may be the cause of Tzar and Fatboy unpopularity (coughsharpshootercoughstarlight), I think the notion of High Trajectory firing modes could be visited to add some needed utility to the Tzar and Fatboy to entice people to build them
I would like to see both these units gain a High Trajectory firing mode that affords them extra range and extra damage at the cost of a lower firing rate and greater inaccuracy. For example, if added to the Tzar and Fatboy, I think it should increase their range by 100-200 or so and add, say, 50% more damage, but have the extra bit of inaccuracy you see in popup artillery when it uses High Trajectory firing mode.
This leaves design space for rocket artillery units, since rocket artillery would still have a dramatic range, accuracy, and burst damage advantage. Even if High Trajectory gave a Fatboy 200 range, for example, it'd still only be 900 compared to an Ambassador's 1300, on top of a much higher burst (800 fat boy, say it was 1200 in High Trajectory, Ambassador's is still 1900), and the Ambassador still has Stealthy to boot
Overall, I think adding this would make them a nice blend of a t2 artillery unit and tough front line aoe unit that would give them a needed buff and get them out of their "cheese" niche where you rush one and then never build another. I could picture Fatboys and Tzars being built to pulverize Sharpshooter and Sheldon balls, for instance, rather than just being outranged with little opportunity for counterplay. It would also follow more naturally from the type of artillery seen in the t1 era of the game, which is all high trajectory by default
Worthwhile design point to focus in on, or no?