To keep the Tier system?

First question that really arises is whether to keep the Tier system of the TF codex or change that to the basic GW system, with a force org. chart and designate all units a battlefield role instead.

the Tier system operates as follows:

PRIME TIER
Firstly, you must decide from which of the Divisios your Archmagos Prime originally ascended from. Known as your Prime Tier, units in this Divisio provide your army with its Elite choices on all of your Force Organisation charts.Furthermore any compulsory Troops choices in your army may be taken from this Divisio.
SECONDARY TIER
With the Prime Tier decided, you must establish from which of the Divisios your Archmagos Prime is most closely allied to. Known as your Secondary Tier, units in this Divisio provide your army with its Fast Attack choices on all of your Force Organisation charts. Finally a single non-compulsory Troops choice on each of your Force Organisation charts may be taken from this Divisio.
VASSAL TIER
With two of your three Tiers decided, it is finally your Vassal Tier which draws on the last of the Divisios that the Archmagos can call upon. Units of the chosen Divisio provide your army with its Heavy Support choices for all of your Force Organisation charts.
FINISHING TOUCHES
On top of these units there is a selection of general troop choices and special units.

Pros and cons.
As I was not planning on keeping all units from the TF codex in the revised version, it would make things easier in certain regards if the units instead had a battlefield role like other codices, on the other hand I could just keep all the units and work my way around it (the initial plan was only to keep the units I'm keen on using anyway). However I do feel the tier system brings a different flavour to the army, but again it makes it very different to other armies/army selection which is a slightly complicating factor.
Atm I'm leaning on ditching the tier system

Any thoughts?