Looks like it. If you want the feature on single board, for ~$10 more you can get one opti-pac. Or you can try hacking two ball mice, if you can find them now a days. But the opti-whiz is such a deal now a days that it's hard to beat, even if you get two.
OT, FWIW, FYI, Warlords used four unlimited (aka free spinning) POTs (after the first batch). However, since it used both unlimited POTs and spinners as inputs, and mame emulates with a dial type input, four spinners is the way to go for mame. So technically you're building a "Warlords on mame CP", not a "Warlords reproduction-just-like-the-most-common-original CP". Yeah, easier to say "Warlords CP", but just posting so no one says "you can't do what you're doing because the original used POTs", because you can do it.