I don't plan to release RZM with a bigger dictionary. Instead I plan to write a stronger version of RZM with support for much bigger dictionaries - maybe I'll give it a different name. I have some very nice ideas to improve compression of RZM without touching decompression speed at all. But this may take a year - because atm, I'm swamped with work and I barely use my computer at home at all.
Nonetheless I do have an old hacked version of RZM which effectively has a bigger dictionary than standard RZM. RZM's dictionary is '64MB' - but due to it's ROLZ nature RZM does never actually use 64MB. E.g. on ENWIK9 the used dictionary is between 4-8 MB. The hacked version doubles this size. Iirc, ENWIK9 improves from 210M -> 196M.
The new version I'm planning will be able to use real 64M - so, it's very interesting to see how far an LZ algo can push ENWIK9.