So I was asked to DM for a group in 4th edition. I live 2 hours away so we are doing 1 12-hour session a month. We just had our first session and I made it clear that I was doing and am willing to do some atypical things. I have only DM'd once before and have only mild familiarity with D&D 4th ed (still more than any of the PCs, 2 of the 5 are 1st-timers).
Anyway, I think that is all important background for understanding the situation I got myself into. During character creation, one of my PCs asked if he could make dual-wielding 2 shields work... and I said yes. So he is a Dwarven Cleric using 2 heavy shields and wears his holy implement about his neck.
Basically, I was thinking that (I may have been wrong about this) back in 3.5 shield bonuses to AC did stack. Also, logically, if you carry 2 shields you would be harder to hit than with 1... After doing some research on these forums I am now gaining the understanding that in 4E that bonuses of the same type NEVER stack (unless untyped, from the same source).
My first question is: What are my options for the best way to handle this situation?
Related question/clarification: Without going back on what I said while he was creating his character, is there a way to make there be some kind of penalty that balances out the extra +2 AC I gave him?
Also, he took a feat to mitigate or minimize (I do not remember which one and do not have his character sheet in front of me) the penalty from wielding shields. Can such a bonus reduce the penalty from a -1 to 0?
Basically... I realize I made a mistake per the written rules due to my own lack of familiarity with the rules. I want to know what my options are but also I do not want to upset my player too much by going back and changing what I did. Also, I have possibly made other such variances from the rules based on what makes sense logically...
The problem for me now is I want there to be some kind of balance in place to mitigate the bonus. I mean... he did take an extra feat to reduce the penalty. But he is still essentially getting +2 AC for free in exchange for not holding a weapon. One thing I have thought of so far is verifying the powers he chose do not have the "Weapon" keyword and only have the "implement" keyword. Also, he will never be able to wear an amulet b/c he needs his neck slot for the implement if his hands are full.
I would appreciate any advice the community here can give me. Thanks!