Just make it balanced. If you balance it then there's no significant gain in power from multiclassing vs. playing a class through to level 20 then it doesn't matter if someone patches together frankenstein's monster because he still can't spotlight steal from anyone else's play style.
Yes, this does exclude the "I want my character to be better than yours" style of player. Inclusion isn't an objective virtue. Broad appeal is, and trying to cater to mutually exclusive desires (A > B AND B not less than A) fails to do so. There are games that cater to either end, heck, look at Ars Magica on the whole Fighter vs. Wizard paradigm.
- Marty Lund
Yes, this does exclude the "I want my character to be better than yours" style of player. Inclusion isn't an objective virtue. Broad appeal is, and trying to cater to mutually exclusive desires (A > B AND B not less than A) fails to do so. There are games that cater to either end, heck, look at Ars Magica on the whole Fighter vs. Wizard paradigm.
- Marty Lund