Do not put any level restrictions on any nanoformulae.
If you can meet the skill requirements you can run the program - This is the fundamental paradigm of AO's skill system. This is what makes AO unique!
The changes to overequipping rules introduced with 14.2 enhanced the skill system - you actually have to maintain a skill level to retain optimal use of your equipment.
Adding a hard level cap to the mix removes a large portion of what makes this game both unique and fun - the ability to customize your character & plan your IP usage, implants and equipment to be able to run nanos a little earlier than the average template for your profession. A large proportion of the playerbase derive satisfaction from this.
If in your (funcom's) estimation a nanoformula is unbalancing to be used before a certain level, then you need to rework the nanoformula - increase the skill requirements or reduce the effect, not introduce some bogus hard cap on when it can be used. If a nanoformula is too powerful to be run on a lower level character, then you need to add a skill requirement for the recipient (much like the bureaucrat charm series checks the target's psychic)
As a Meta-physicist my primary role in a group is to temporarily enhance the nanoskills of the team & allow them to use higher quality nanoformulae, thus increasing the team's effectiveness while my nanos are running on them. Adding a level requirement to a nanoformula totally and utterly negates this ability & impacts severely on the usefulness of an MP in a team.
You've said:
By that logic there is no need for a hard level requirement on any nanoformula.When these new nano programs were created, a level was picked to determine when the nano program should be used. Skills are then chosen, based on that level, and not assuming you have maxed implants, maximum items and maximum external buffs. A percentage of this was chosen, and the skill requirements are the result.
If you're intent on introducing a paradigm shift of this magnitude, then you're destroying what makes AO the game it is. A wise man does not level the playing field by bulldozing his own house.