There are already rules for spam with appropriate punishment for violators;
Staff do not want to hand out bans for unconstructive posts but if we feel that you as a user are continually making very poor or unsubstantial posts due to your paid signature the following bans will be issued:
First offence: 7 days
Second offence: 14 days
Third offence: 30 days
Fourth: Permanent ban
About your suggestion; While deleted post usually means it's spam, making a general rule regarding that may not be advisable. Some users complain of their bumps being deleted wrongly or their replies getting deleted mistakenly for some other reason that isn't spam.
I believe it's best to handle each case uniquely, rather than taking a general approach.