Conventional wisdom might suggest that technifying rec diving would make it safer but part of the safety of rec diving is that it is not tech diving. Some believe that placing artificial barriers on rec diving actually acts to take away some of that safety.
There are various ways of teaching people to do things. You can simply give them a set of rules and tell them not to break them. That'll work pretty well with the people who are temperamentally likely not to break rules.
You can give people a set of rules and explain why the rules are what they are, and what the consequences of breaking them are. That will induce obedience in some of the more thoughtful people.
Neither approach gives the student any tools to cope with a broken rule. And humans being what they are, rules are likely to get broken from time to time, even if that isn't planned.
But you can give the student a set of procedures and explain that these procedures apply to a subset of the possible situations the student might encounter, and that it is desirable for a student, with limited experience and training, to confine his explorations to those situations. If you also recognize that there are scenarios outside those protocols, and give the student some basic tools to cope with them, you will avoid the "OMG I BROKE A RULE" panic response, which we have seen written up on this board a number of times.
Deco isn't death. Tech divers do deco all the time. The reason recreational divers are told to stay out of deco is not because deco is horrible, but because recreational divers don't have the planning tools to know that they can do the deco they incur (gas, thermal protection, redundancy) and they may very well not have the diving skills to actually DO the deco (hangs in midwater with no visual reference, or a stepped profile that requires precise buoyancy control and timing). It is my understanding that CMAS includes some backgas deco at their higher levels of recreational diving; GUE teaches a "deco stop" approach to recreational dives, to make the transitions from no-deco to mandatory deco a pretty minor change.
I don't think the OP should plan to exceed his no-deco limits. But he is asking the right question -- IF you end up with a deco obligation, how do you know how much gas you need to execute it? I'd much rather see a recreational diver look at his computer and say, "Oh, drat, I went into deco, I'd better deploy my 40 and do my time," than have someone look at their computer, recognize they're in deco, have no idea what they need to do now, and panic -- it's happened, and people get hurt that way.
Kudos to the OP for asking the real question -- if you have the gas, you can do the time.