Considering our gem-resources are limited: there is a relative increase in personal investment, would non-VIP members be able to contribute more.
Therefore I do believe limiting us to only a 10.000 coin investment per day is a little excessive in trying to get people to go VIP.
I'm not saying to open up both Decent and Grand investment, but maybe open up Decent and create another category in between.
By creating something like a Significant investment to be VIP-limited with Grand, there is still a lot of buyer-incentive,
but it would allow for a more even playing field for Guilds, considering there is no guarantee the VIPs are evenly divided over them.