First off, NOTHING is easier than the set of tools Roland provides, so no this is not as easy.
It really isn't that difficult, sorry if it came across that way, but it is a bit time-consuming. You do need to create a patch map the OMB can use to access the mega sounds in the racks. Then the style parts applicable need to be edited to use this map, and of course because only one map can be in use within a particular style (and indeed the overall operation of OMB) you also need to ensure the map also contains all the correct data for the other instruments the style uses.
Now this presents another set of problems because the patch map needs the cc 0/32 data to point correctly to the preset bank that contains the mega voices.
BUT this cc0/32 data is then incorrect to address the "normal" sounds required like strings or bass or brass or whatever, which is based around the Yamaha maps used on the PSR/Tyros keyboards.
I cannot remember enough about the Tyros/PSR 0/32 data to give you an example, but it IS different to that required to address the Mega voice bank on the racks.
Essentially you need to incorporate a few different patch maps to get say, one part, of the style to use a mega voice.
You COULD load up an INS file for your Roland banks and access the guitars in it, along with the drums and other ROland patches. Essentially running the Yamah style, but using the Roalnd sounds.
BUT, (alwasy a but
) this then presents the problem of the Yamaha style "bloat" which noticeably makes the style lag, mostly between fills and changes of variations. In fact when using some of the later styles this is even to the point where the entire style hangs for maybe 150-200ms.
Some of which, as I recall are pretty good with differing velocity layer ambience effects???
So as I said its not particularly difficult but it is awkward..to the point of not really being worth the effort for one sound. Well, for me anyway.
FWIW, I am about to get a new laptop, and I am going to give the new version a whirl, so if you can wait, and IF you are interested I can give you my views on how it works.