Genghis,
It isnt clear from your posting whether the FISO got a correct acknowledgement to his second attempt to get the PA28 driver to understand his information about your presence. If he did get a correct reply then the PA28 driver appears to have not really understood what was said or just plain didnt see you until it was too late.
Also from your posting it would appear the PA28 driver was of advancing years. Not wishing to run down our elder members but I do sometimes have concerns regarding old age pensioner pilots, particularly those who have had a lot of past flying experience. We are all going to get old one day and its a straight fact that you do not remain so mentally nimble as the years advance. You can rely a lot on your past experience to keep you out of trouble but when things start getting out of shape oldies are often slower to react. When they drive cars on public roads they normally drive more slowly than the youngsters so that they can assimilate the information they are receiving and still have time to react.
As for mixing different types....well there is a limit to what can be mixed. If you get some large machines flying around you have to allow for vortex wake as well as speed differences. This can totally disrupt a nice orderly circuit pattern.
Regards
TMC (getting older every day)