If you only want one toon....

Consider doing RAF with one of your five accounts.
Linked to a brand new account, which is only wow classic.
Boost two toons (one on your existing account, and one on the new account), to 60th.

When you pay for a month on the new account, it credits the referring account with a month.
For a net gain/loss of zero.

Then you have the choice of transferring the toon on the new RAF account to one of your accounts.
Or just leaving it where it is.
But you'll have a new healer (shaman) at 60th, having leveled there with RAF speed.

At which point, you can discard the new RAF account (don't upgrade it from classic/original wow at all).
And level your 60 or 60's however you please.