It's not the result that was surprising, but gulf between actual strength and match ratings when a team employs off-position tactics. There really isn't an effective way to gauge off-position strength, apart from watching the game and seeing how well each player does against his opposing counterpart. It just triggered a discussion on the merits of off-position tactics on offense, while retaining on-position for defence.
in the PL I am currently playing, we did some trials about mispositioning (C switched with PG in starting position, with defensive switchover): results will require some more analysis and trials, probably me too I will try something about.
depending on offense and defense, switches create opportunities. However, they are not so many, and, apart of what was called "insane" skill mix, your offensive bonus (depending on evaluation) will be impacted directly by misposition. If your C has 15 in IS and your PG an even good 7, your offensive evaluation and consequent bonus will be far lower. On the other side, you will have more mismatches. I noticed it too when last week my coach replaced my broken PG with a PF (with decent secondaries, luckily): he took many good shots!
although I use changes, forcing positions (in SA U21 too) to stress an offensive side of the attack, this is a bit too extreme to me. first, if you build a team with some rationale, it is hard to avoid bonus penalties when switching players so hard. second, if you have not a good offensive flow, your shots will be probably forced and you will probably increase lost balls. at least, that was what I noticed.
in some cases, I think you can try even to have 4 Guards and 1 Center in your starter list and attack with hard R&G. It is similar, although not as much effective in defense (but better offensively).
As per few observations, the advantage you can get out of change is not enough to compensate disadvantages. At the end, our feeling was that you didn't impact much on final result. But more trials will come, let's see.