Jump on TeamSpeak and talk with the players running the champ spawns, they have let me join them many times simply by asking. Usually look for a bunch of players in one of the various public channels.
We will not yell at you for asking to join in on it, and usually a pretty good crew for the most part.
Even for the Fel champs, just do not run in at the last minute and expect to not be attacked since they will be expecting players trying to ninja a boss at that point and trigger fingers get itchy. If it is on the last candles before the boss spawns do not jump in.
Do not camp a spawn site, AFK, ghost, or while invisible. Especially in Fel, someone may use you to raise their snooping and stealing skills before killing you while your AFK.
Here is a helpful link from the wiki as well. List the locations and directions to find the various champs spawns.
http://www.uoevolution.com/wiki/index.php/Champion_Spawns
Also as a curtesy to others be sure to clean up the creatures left alive after the event please. Annoying to be traveling through an area and suddenly run into a wall of claws coming at you, lol.
Go through the listing in the link and make yourself a rune book for them, if saves a lot of time. I will be working on that this weekend, myself, finally.
Now to address the OP's suggestions. I do admit it would be nice to be able to receive power scrolls while in the safe areas, it is one of the few bonuses players receive for adventuring into Felucca for these events. If they changed it, so that Power Scrolls (PS's) were received in the safe areas I would recommend that they offered as a reward of 1 PS's at 105 with a 10% chance of receiving a 110. Also, if possible, remove the 105 and decrease the chance of receiving a 110 when completing a Felucca champion spawn, while keeping the existing rates of the 115 and 120 PS's.