It might be worth a consideration to allow players to buy more spec sets/slots and maybe even expand this mechanic to skills as well and then allow some command based switching between specs. Given that respecs are a quite sizable feather sink the cost to permanently unlock a new spec slot would have to reflect that.
Major downside however would be the lacking client support meaning respeccing would break your quick bars. In case of RAs I'm currently unsure if it's limited to just having dead / wrong buttons for things representing RAs you no longer have or if it would affect all of them e.g. even if you have purge in both sets it could still be broken on the qb if other actives changed between the sets.
For skills it will most likely be even worse but not entirely how bad exactly meaning you'd still have to "pay" the quickbar setup cost.