This is what I would do to help make classic more "new" user friendly
1) Remove the magic stone cost from all classes. It obviously isn't doing it's job
2) Offer 1 week VIP. Maybe 200 WPE or something. There are a lot of people who cannot play much during the school year, and offering 1 week packages when they get a light week or something would incline them to play.
3) VIP buffs/Warps. Make the x3 EXP buff have a 30day cool down, last 1 hour, and can only be gotten when under the effects of VIP. Offer the dungeon warps at a cost ( upper tier dungeons = huge zeny cost, will be a decent gold sink )
4) Up server rates and nerf thors. When I say "nerf" thors, I just mean keep it the current exp rates, while buffing the rest of the game. Maybe put the server at default x2 instead of 1.5.
5) If your not willing to do 4, do this. Lower the exp curve for 80-99 trans. I feel like this where a lot of new players quit.
6) Offer lvling up boxes, with bound items. Maybe around 90 or so offer a bound item such as a +6Hurricane Fury[1] for Smiths, a +0 Infil [1] for Sinx's etc. Would help give people the gear they need to compete, and wouldn't be "too" overpowered. Maybe offer some other bound gears as well.
Now in terms of offering guilds the "ability" to transfer/join classic with insentives, I feel that it COULD be a good thing, but the insentives you would have to offer would be too high ( ability to transfer lvl99 non trans characters for example ) If i were to offer insentives this is how I would do it
1 lvl 85 character
Full set of rental gear ( lasts 30 days )
Full set of +5 Secured gear
1 Weapon Box ( Choice of one of the following: +7 Jur[3],+7 Oricish Axe [4],+7 Survivors Rod (Dex) [1],+7 Chain [3], +10 Pike[4], +5 Orc Archers Bow)
30 Days VIP
1 Emp
30 Kafra Teleport Tickets
30 Kafra Storage Tickets
1000 White Pots ( weightless)
500 Blue Pots ( weightless )
1000 Fly Wings ( weightless)
1 Neutralizer ( bound ), has to be used before trans