I think on deletion of a character you could incorporate both options in aspects. On attempt of deletion you would be given a warning about not having enough plots on the remaining characters to cover the current placed plot count, ‘Are you sure you wish to delete? This will place you in a negative plot count, you will not be able to plot again until you have earned enough plots to recover your debt.’
With showing how many plots you will be in debt and all plots costing 30cubits each, there could be an option to use cubits to negate this debt at point of deletion for those who may have cubits saved up.
I will agree that to have the ability to have account wide plot balance instead of character based would be a huge QoL change for some who have played as 1 character and since moved on with random useless amounts of plots that now sit wasted.
I would say that to have it as account wide plot balance would be better as an option rather than a guaranteed thing, for families where the parents don’t necessarily want their children running round randomly spamming their plot count everywhere. This would keep some control and maybe avoid unnecessary reports about people mass plotting against people causing issues and taking up valuable dev time resolving these if they can’t be handled between players.
All in all I feel this would be a good idea as an optional setting.