Multiple Roles in One Company & Resume

BLUF: Is it ethical / acceptable to combine two progressive-in-title roles into a single role on the resume when there isn't a noticeable external difference?

I worked at a company for 11 years and held multiple positions in two different business units. At one point, I was promoted from Individual Contributor to Manager and then went back to the Individual Contributor role (in lieu of layoff during a reorganization) - as outlined below. The Individual Contributor roles were not terribly different from one another and the Level 1 and Level 2 roles were barely noticeable changes, pertient mostly to internal dynamics and seniority. I don't even know that there was any real change between Level 1 and Level 2 in terms of expectations. I'm sure there were, on paper, in some obscure corporate terminology but in reality, you didn't get the Level 2 title until you'd already been working at Level 2 for a time while still technically in a Level 1 title.  (You'd get progressively larger clients or more complex accounts the longer you'd been in the role but again there wasn't a switch or formal hand-off from one role to the next. I was largely doing Level 2 work for half the time I held the Level 1 title.)

I know the Resume Workbook says that "the responsibilities will have been different and therefore each will need a separate section on your resume" but again, the responsibilities were the same and the progression between the client base or complexity is largely insignificant to the outside world. Additionally, I note that the workbook says "if your title is meaningless outside of your company, then you can consider using a role title which is meaningful in your industry ... to make yourself understood."

Part of my challenge is to show progressive responsibilities while trying to "fit it all in." My Career Management Document 17 roles on it going back 27 years. And at least three of first roles I held are still relevant today - dealing with unions, employee benefits, designing methodology, etc. - so I'd like to be able to have them appear on my "simple one page document."

Sample Roles Within One Organization and Two Business Units

BU #2 - Role 1 - Team Lead

BU #1 - Role 6 - Team Lead

BU #1 - Role 5 - IC Level 3

BU #1 - Role 4 - Manager

BU #1 - Role 3 - IC Level 3

BU #1 - Role 2 - IC Level 2 - roughly the same as the previous role - slightly higher dollar value & complexity

BU #1 - Role 1 - IC Level 1 - roughly the same as the subsequent role - slightly less dollar value & complexity