since this is the 'drafting techniques' forum, please excuse me while I go off on a rant.....
Controlling object display on a per-entity basis, that is assigning a color, lineweight, linetype, etc to each and every object in a drawing, is IMHO one of the worst possible things you could do. It's even worse if you collapse all of the layering structure into a single layer. It becomes impractical/impossible to repurpose the drawing or to xref the drawing, to reuse or recycle the design in any meaningfull way.
The drawing is instantly non-portable, and will be a horrendous bear to work with both now, and down the road when that job comes back to life, or if the information in the drawing needs to be reused for a Phase 2, or addenda, really for any other purpose other than the original. No-one works in a vacuum - every one dealing with CAD is involved at some level of collaboration with other users, and no drawing is ever guaranteed to be never needed again.
If the goal is to waste time and money, while concurrently making the design information useless, then the approach of collapsing layers and doing by-entity control of object properties is an excellent technique and a great way to sabotage the end product.
it's not however, a 'drafting technique'.
+1 on the hazards of removing layering.
IMO, the layers themselves are not causing the drawing to be 200% larger than than it would be with a single layer. Isolate the cause, rather than destroying the drawing.
WAG: extra layers from annotative objects via the SAVEFIDELITY setting, along with lack of annotation scale control. Extra layers, extra objects, bigger file.
Overall, yes - fix the actual problem. Its like putting a bucket under a roof leak. The problem isn't that the bucket keeps overflowing, its that the roof is leaking.
OP you never did say what sort of CAD files these are or what business you are in -- civil? architectural? structural? mep? machine design? what?
Is someone else requiring you to reduce file sizes? or have you decided on your own? Are there others that also access your work and use it too?
If I were you I'd explore other options before taking the radical step of putting it all on one layer. These are people here with lots of collective experience trying to tell you "Don't do that!" and for good reasons.
If you use Recover to open a drawing file, and then purge it and save it, you should notice some improvement. There is a command line -purge that has more options to purge, such as regapps.
In addition you can write the entire file off as a new block (a separate drawing). That will get rid of a lot of extra stuff too.
Do you use XREFs? If not, then explore what they are and how to use them. There are settings that only read the portion of the XREF necessary to the drawing it is XREF'd into.
There are lots of other suggestions if you search this site for them. But for heaven's sake don't put all on one layer. That's a Freshman error that's right up there with moving things with some layers turned off!
Log into access your profile, ask and answer questions, share ideas and more. Haven't signed up yet? Register
Start with some of our most frequented solutions to get help installing your software.