Yes, I know that some of the Spanish companies (like Opera) where using a PC (I think it was a PC) to cross-compile for many 8 bit systems. However, this was in the final years of 8 bit development and the problem was that the kit, as far as I know, did not take advantage of the particular characteristics each the machine. I remember reading that the deadlines, and therefore the recycling of the code, were one of the main issues back in the day. The companies used to give programmers very little time to develop the games and they reached the market even with bugs in some cases. You can read more from a real insider here:
http://www.cpcwiki.eu/forum/games/rastan-coder/In that regard, La Abadia del Crimen was an exception. Paco developed the game he wanted to create and only when it was finished it was offered to Opera for the distribution (I hope my memory is not failing me). This made a huge difference.
P.D: I also forgot to mention that only a few games of the old times take advantage of the extra RAM in the 6128. This did not help either, but from a commercial point of view the games had to be as compatible as possible. I remember to hear that in some cases it was necessary to employ compression techniques that were killing a full 1 Mhz, or more, in the Z80.