Actually editing entities is ambiguous at best.
As there's no difference if you edit a map by mod (adding gametype and dropping a rule (flag, spawn point..)) or by altering property of the source, in either cases it's the same. But it's debatable yes. I personally don't see a problem if one edits the map in sense to fix what designer done wrong or to suit his own agenda (new gametype etc) as long as one doesn't claim to be the author of it or does anything that would strip original author out of his credits in any way. But I fully understand that some authors don't want no one to meddle with what and how they done it.
As for entities editing, it applies on all rtcw as well as quake3, (probably even jedi and other q3 powered games) and other games. Brushes are hardcoded so you cannot alter static stuff (world in general), but you can easily hook a trigger under existing brush, alter it's behaviour to achieve your outcome. For example in SP village2, you modify SP end game and hook "trigger_flagonly" entity, which will once documents carrier is there, thru script call the game end, in that sense you can hook it almost under any existing brush in the world. I could easily edit any coop map and change where soldier spawns, it wouldn't make any sense since it's already controlled by ents and other scripts but I could, if I would want to.
As for cappuzo. Tbh it's not a rush thing, I only asked for source because it may take a year or more before I even reach the stage I will want to address mapping so by that time you may be long gone and unreachable. I mean, idea of wolfX later on is to replace all assets..that means that all the default maps will be lost, so I'll have to present new alternatives. I could redo default maps but what's the point? I think wolfX should follow it's idea and present new maps and tries to surpass current ones (mp_beach, mp_base..). While it's pretty much an impossible task to surpass something that's a leading factor for decade, but hey, one has to try I guess.
As for mapping it self. To be completely honest, I don't even want to deal with it at all. I rather see that someone else does it..but I only know handful of mappers and most are either uninterested or are doing other things so I don't even approach them. If you have the interest in mapping for wolfX once it comes to it, I'll gladly accept any help..but like I said, that's quite far atm as well as, I don't really want to bug people that have other things to do..thus given task to my self to do it, once it comes to it.