Maybe some of the problems they had when the PCL basketball championships were at LaSalle have had something to do with LaSalle's lack of interest in making some upgrades to McCarthy and then renting it for PCL use.
I just looked, thanks to Google, at the site of the old Cahill Field on 29th near Clearfield and it looks like it's a vacant large lot. It was used (and owned?) by Roman for many years and was big enough to accommodate about 10,000. The problems with this site and the many others like it within the city are 1) parking and 2) safety and security. Solving #1 could help with #2 but some people will still want/need to take public transportation.
I suppose there is also the question of what the future holds. I've long thought the Archdiocese should take a property it owns in a relatively central location that is no longer being used (Hallahan?--though that property may not be big enough) and consider making it available to several PCL schools (Roman, N-G, WC, and SJP?) for their home games--meaning that on an average fall weekend it might be used both on Friday night and on Saturday. It could be seen as a way of promoting Catholic high schools. Of course, some of those properties--certainly the Hallahan site, which may already have been sold--could fetch a good price on the real estate market--and we all know the Archdiocese needs money. There's also the issue of how many of the high schools will survive for 5, 10, or 15 more years and, if they do, whether they'll all have football teams and football teams that get much support.