It seems very clear now that the only thing that can be done to reduce alts, is reducing the necessity of them. I've thought of a way to achieve that:
Make death causing loss of a fixed amount of LP and FEPs proportional to your highest skill and attribute (and not a percentage). That way, the loss will be about the same if an alt or if your main char dies. This amount of LP should be relative to your highest stat. For example if you have a crafter and a farmer alt with the same of the respective skill, the loss of LPs of one dieing will be the same compared to a character that is crafter AND farmer and dies.
As I think of it, the amount of LP lost should be roughly equal to the amount needed of your highest skill. (for example, if you have 100 UA and 1 to everything else, you lose the 50k LP needed to make the 100UA. If everything is 100, then you still lose 50k LP.) About attributes (FEPs), things might be slightly different: Because different jobs usually require more than one attribute, maybe there is need to reduce them more after death (But still fixed amount of FEPs relative to the highest attribute). Anyways, I'm not sure about the exact amounts, but you get the idea.
For players that don't use alts, this will make a player that is, for example, farmer, crafter, smither, to lose 1/3 of his work. For someone who has 3 alts, a farmer, a crafter and a smither, a death will also be roughly 1/3 of his work (if they are equal). This doesn't completely elimitate he advantage of alts, but it reduces it significanly.
I know that the above makes death less destructive for people that doesn't use alts, but it doesn't make any difference for people that use alts. In short, it gives all players most of the benefits of using alts, without needing them to use them.
You might ask, is that good? Well, lets be honest: If a countermeasure against alts (like the one I suggested) is not implemented, then at the end, some people will still manage to make alts and will have a huge advantage against casual people who, especially now in hafen, just don't want to bother traveling all the world to find alts. That makes casual players totally unable to compete. Since the new spawning system doesn't completely eliminate the alt problem, I think it is necessary to reduce/ eliminate the advantage of having them at all costs. Otherwise there is no point to just make it harder to make alts.
Any thoughts on this matter?