I can't answer the questions about whether or not it's worth it for your team to design and implement sliding bearing blocks, because I don't know your team.
In the past, my team has used bearing blocks attached to screws to tension our chain without decreasing efficiency: (
http://www.youtube.com/watch?v=MgYnw...XrOpK1&index=2)
It's one of the best solutions for maximizing efficiency in a drivetrain, but the process is very machining-intensive. I'm sure your sliding bearing blocks, while not as complex to machine as our tensioning system, will have similar pros and cons that accompany any machined part that isn't flat.
I recently had a similar discussion with one of my friends, and he brought up a profound point.
"It's not about the numbers, it's what you can do with them."
I'm not going to pretend that I've done the math, so here's just a ballpark estimate: Say you're losing around 5% efficiency when adding 18t idler sprockets that you bought for 6 bucks each from VexPRO (great value, by the way).
Is it worth the machining time and design time to make your own tensioning system? Are you confident in your ability to get it right the first time, if you haven't prototyped in the offseason? If your machining time is limited, would time spent by making the bearing blocks be better spent by machining parts for your end effector? I'd ask more questions, but I think you get the point.
If you want my honest opinion, I think that our chain tensioning system is a bit convoluted and unnecessary. I would say that using idlers isn't a bad option at all. Heck, 1503 in 2011 and 1114 in 2012 (IIRC) used dead spaced (not tensioned) #35 chain runs on their drivetrains, and you know where they ended up. It's really a matter of preference.
If you know your limitations, you know your budget, you know your sponsor's capabilities, etc, and you decide that the boost in efficiency is/isn't worth your time and effort, then make that judgement call.
Remember that time is one of the most scarce resources during build season. Use it wisely.