Well that's a very interesting concept, and most of the overall weakness in cricketing statistics that they often don't reflect the match situation.
However, getting a better reflection on how "important" your match performance can work in the opposite direction and removing weaker sides from the equation isn't the answer.
Firstly, there is the issue of being able to capitalize in the right situations as oppose to scoring when it is easy, which we count and which we don't.
Which innings was easier, for example - Jonathan Trott's hundred against Bangladesh, scoring against a poor attack but early in the game on an early-season English wicket while under personal pressure to deliver - or Matt Prior's hundred at Sydney, coming in with the aim to stamp a half-beaten and demoralised attack on a flat deck.
It's not as simple as it sounds, so why do we pick so easily?
Then there's the matter of what those playing for a weaker team might achieve. Take Shakib Al Hasan for example. In your post you used the slightly unfair qualifier "test-standard" to distiguish against his performances in ODIs against Zimbabwe or Tests against a depleted West Indies unit in 2009.
People who remove Bangladesh from averages might have removed that side too. But for Shakib, he was going on tour with the first reasonable chance he has ever had of winning. The runs and wickets he got there will mean a tremendous amount to him and indeed he had a huge effect on that series. So by your own standards those are the runs that count the most.
Conversely, suggesting that performances that don't affect the match situation don't count could suggest you'd remove Shakib's excellent bowling effort in South Africa. He never helped his side win, they never even came close. But you would have to admit it's unfair to take that series away from him personally.
It's not just Bangladesh of course - would you remove the stats of, say, Vaughan in Australia, just because his runs didn't effect the outcome of the series?
These are obviously delicate and trying to adjust the stats to reflect the competitiveness is clearly a lot more complicated than just removing Bangladesh from the equation. So we have no choice but to keep them in.
