I think the negetive xp bonus is not very friendly to people who have been playing for long periods of time. I wouldnt want to retire after level 5 or six if I knew it was going to take me 5 times as long just to get from 1 to 30 again.
Not to mention that by giving out negetive xp, you will effectively soft cap the retirement levels. there will be a reachable point at which you will no longer be able to level up at all. It isnt supposed to be harder for succesive generations to be able to actually use the hierlooms daddy gave me, if you know what I mean.
I, personally, look forward to retireing a few more times so that the peasant grind will get shorter and shorter. Not longer each time.
Instead of killing our current bonuses, just re-implement the time limit on the retirement feature. Say, five to seven days per.
High levels can still get back up to 30 in a day, and it will encourage them to level up more alts while they wait for the ticker for retirement.
You shouldnt be punished for putting time into playing the game, as the negetive bonus reflects.
Just even the playing field, dont punish the players.