All top end arrangers have the capability to add new sounds or edit existing ones, a drum kit is just another sound to the keyboard, (The drum sound produced is determined by which key is depressed) so just load in another drum kit that you like the sound of.
The onboard drum editor allows you to alter the overall sound of the kit, each individual instrument or even change the instrument, (A good way is to mix and match, IE Standard kit replace bass drum with one from the jazz kit etc) although you will probably need to alter the attack, decay, reverb etc, to get the kit balanced.
If you have a sampler or you can load in samples, then there are plenty of free drum samples on magazine cover discs, which you can either use to make up your own drum kit or mix and match with an existing drum kit.
From the above you can see that you can achieve probably 95% of what a workstation can do, but it will just take longer and you will need to set it up before hand.
Workstations have the advantage of making things easy to edit, but take a considerable amount of time to set up, consequently your gig has to be predetermined. (Audience requests just aren’t on)
Top end arrangers also have style editors. (or allow you to export the style as a midi, allowing you to edit it in a sequencer, and then import it back into the keyboard as a style)

Bill