Hi Vojislav,
This is interesting indeed. I have done this in the past in an MSA environment where everything was on wondows and we added a node having ASE on Linux and the database was synchronized using dump marker. All versions were in early 15, ASE 15.0.3 for sure ,RS maybe 15.0. We did it while the users were working, however the activity was not heavy.
Concerning the cross platform dump/load in practice I have seen many times this process working without having quiesced the databases, however sometimes it doesn't. Ant for sure it is working if there is no transactional activity while dump is running. I also think that endian plays a role here.
I shall check again the manuals also on this.
Best regards,
Kimon Moschandreou