Pretty much, we have a couple of options.

Align spells with similar effects, recast delay, or cast time... so you can push a few DPS keys, and get the desired effect. This gets you the most control, and is the least likely to ever need to be fixed again in the future. It also forces more micromanagement of your team and abilities.

Another option will be to build the best castsequence you can. Even if it is not as optimal as click, encounters are balanced so the majority of the player base will eventually beat them. That means, a slightly sub-optimal DPS sequence combined with a boxer being smarter then average PUG player, will likely be good enough for most/all encounters.

Most of the software options have the equivalent of Steps. As in, you push the key once and it sends a given output. Push the key again, and it can send a different output. This is how we build round-robin effects, on the software side. The same mechanic could easily get a castsequence well beyond the number of spells you'd be able to include in a warcraft macro, if you choose to go that route. Not sure it is a good idea to use software to circumvent something Blizzard is blocking, but even if we don't go that route, we have the tools to be rather creative in how we end up DPSing.

Also we can do a hybrid approach. For example, put the "proc" type effects on "2". And have a spammable castsequence on "1". Then the DPS spam might be: 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, or whatever else we want it to be. Again it will depend on the classes in your group, their spec, and how important a given proc is to hit.