What is unclear about the Article 50 procedure? The divorce bill perhaps? But what else? 2 years to come up with a better plan than a hard divorce, if not a hard divorce it is.
The divorce bill needs clarification, the commitment of 28 must become that of 27 in Mar-2019, projects are not fully funded at inception, the cost is agreed and paid in stages. The commitments should follow the budget principle, the UK has to foot its portion of the cost to the exit date. Discussions can be held about whether either side will continue participation to project completion, but one cannot demand that participation and use it as a block.
Your question of 2 years to come up with a better plan than a hard divorce, there is no such thing, you are a member or not, full or Norway, what is there to negotiate? Any member leaving the union becomes a third country on the date of exit, both the EU and the UK deal with third countries, both sides know what it entails. The UK may have made some major mistakes, if EU red tape is an impediment to trade and business, why accept all EU standards into UK law at Mar-2019, is that not one of the reasons for leaving, the 2 year period should be defining the new rules. In an earlier post, trade between the two will decline, allowing it to continue for ease of business for a transitional period will ensure that the business who will ultimately relocate, do not contribute in any significant way to the building of the "new country", that is the flip side of the so called cliff edge. Just as business houses do not want to curtail the huge bonus payout to executives, they do not want to pay the necessary higher tariffs that have to come to fund the new country. The UK has to pay for its expanded infrastructure, as an example, if a EU tariff of 7.5% is charged, WTO is 10%, a 2 year transition on Mar-2019 sees an increase to 8.5%, if at the end of the period no agreement is reached, continue as is or go WTO. The good thing is that so many examples of tariff rates already exist and are being used for trade with non-EU countries, both sides agree on which one to use and customs fees issue resolved. Product standards must also change which was another Brexit vote issue, so far the UK has spent little to no time on their standards, they achieve no cost savings if they blanket accept EU standards for a transition period, any exemptions or UK specific aspects would be gone, that may increase rather than reduce the cost of business.
Freedom of movement is also a core principle, you have it or you don't. Simple plan by the UK would have been that all EU workers automatically receive 2 year free work permits on Mar-2019, after the end of the period, they would be terminated or renewed by the company, having a cost associated during the 2 year period lets all see at a glance the financial impact, if housing etc is also included that also follows the 2 year rule. It works like this outside of the EU, no need to re-invent the wheel.
Non-workers, the plan set out by the UK is viable but open to changes and adjustments, that is where time can be spent in negotiations as the mandate are different. The UK would be making persons citizens of a country, the EU can grant EU access but I don't think they can grant citizenship to member nationalities, I suspect each of the 27 have their own requirements.
The major problem rest on the UK side, the politicians and elites (business interest) were mostly remain, as such the current government is mostly remain, I agree on the nostalgia part, but it is the wrong nostalgia, it is not of past colonial days, it is the remainer's wanting to cling to the past 40+ years of EU membership versus standing on their own two feet as the citizens demanded. Millions voted leave, to say they were all delusional or led up the garden path does not bode well if they remained in the union, they would be fodder to be trod on or cost millions in re-education programs, as no one will be trying to figure out how they got that way.