Propose for a minute there is a constant difficulty: What would happen is that block rates will be accelerating hash rate which would result in increasingly faster transaction times and more inflation. However if the hardcoded block reward decrease is kept the total number to be issued will still be limited. On the other hand there would be no early adopter benefit except the within the scheduled adjustments of the block reward.
Of course this has some obvious disadvantages: The block rates could get so high that network latency and orphaned blocks becomes a serious issue. This would lead to increasing centralization of mining and thus creating a trust problem. At some point even the speed of light becomes an issue making orphaned blocks a certainty.
Liquid coin conforms to this idea i believe...
Difficulty is fixed at 0.5, and block reward decreases (exponentially over time... or block? sorry i forget the exact maths)
I believe there are a number of orphaned blocks in this chain, most likely from what u describe, but I have not looked into this fully so other users may be able to provide more info
have i interpreted your suggestion correctly?