Can you make there be a perma version of these mounts, as the only mount covers cost RP? Make them cost 5-10x the expiring mount cost. Would be a nice thing to work towards for individuals who are tired of their pig / drake mount. Just an idea.
My idea would be to make this another meso sink (everyone's probably tired of seeing this phrase). This would be similar to the cosmetic coupon at CBD if I'm not mistaken but to a highly scaled up version. I've got a few points to make this as detailed as possible. 1. Not a gachapon The reason why obtaining perma mounts should not be in a gachapon system is simply because the variety of mounts is very limited (relative to the variety of scrolls/equips/chairs). Given the limited variety of mounts, players can buy the mount that they want without an RNG factor. 2. Untradeable For it to be an effective meso sink, it should be untradeable. If it were tradeable, these mounts will just get passed around infinitely and the idea of a meso sink is no longer there. 3. Make it expensive Now 'expensive' is subjective - it varies from player to player but I feel that permanent mounts should be a way to flaunt your items. The idea is just like chairs. Players with a huge meso pool to expend on luxury items that have no effect on gameplay can use mounts as well. For the more expensive mounts, maybe price them at 500m? The cheaper ones at 200m? Just giving numbers here. Those are the points I can come up with. I believe this will not have a crazy ton of mesos sunk compared to chair gacha but at least it is an avenue. More avenues, more sinks and the server's total meso will grow not as rapidly. Furthermore, this is a F2P server. For those who do not choose to donate, at least they are able to get the mounts which were completely out of their reach in the first place and alsostabilise the economy a little. This idea however could somewhat affect the total donation to the server but hey at least the economy may be controlled? It's a give and take. Something has to compromise.
There are a couple of reasons for these event mounts being temporary. One is that there are quite limited item ID slots available for mount covers, and therefore the same item ID gets replaced with another event mount cover in future events once all previous once have expired. Another reason for them being temporary is that if permanent they could make purchasing of RP mounts much less appealing. Currently RP mounts - although quite expensive - are a very appealing purchase to donators, and so is quite a large source of income that helps keep the server running. There are actually few non-RP mount covers available in the Cash Shop under the Package tab if you are sick of seeing a Pig, Hog or Draco.
I have an alternative idea for your needs. Make an, either nx or meso, random temporary mount package, not higly expensive (because of the random factor) but not too cheap either. With such package, you'd have a specified rate of getting ANY of the mounts available in the server for a specified period of time. Rarer and donator mounts 1~15 days, event and common mounts 15~30 days. They must only expire after the first use, and it must be untradeable (not only the mounts but also the package if it comes from nx) So whoever wants a different mount cover would have to gamble in this package, and wouldn't mess with the donations a lot since they'd be temporary.
I appreciate the insight as to why they won't be made permanent. Was just an idea I had since the halloween broom mount actually looked nice with my character.