I've been writing my own RPG, mainly to address some of the flaws / frustrations I've come across in other games. Luckily, I've found a few willing participants to help test the rules and mechanics in mini play tests, but this has lead to two problems:
Some mechanics quickly appear broken - should I rewrite the rules on the fly (likely to not be that well thought out) or skip over the mechanic entirely, or "GM" override the result.
An example of this situation was where both the PC's and NPC's couldn't hit / damage each other - the odds were far too remote.
Not all the player actions have been anticipated, so how do I constrain the characters actions without, without stomping on their idea / enthusiasm.
In this case, the combat system was similar to D&D / Pathfinder, but I hadn't limited the number of "attacks" of opportunity, so as a gang attacked the player wanted to keep reacting out of their normal round action.
Apologies for the questions being a little woolly, I just really like some general suggestion on how to deal with any rules that are obviously a work in progress?
Advice from anyone involved in any RPG, regardless of system would be very welcome. Does the same situation apply when people create add-on content for established RPG's like D&D?