I think it is much more than just about the money for the rooms and only allowing admittance to guests who stay over. It's the principle of being told where to stay which is the real issue - even people who could easily afford it, or are prepared to pay, may be offended at the venue's ridiculous rules.
I have only heard of this once before at a wedding and I think many of the guests did not quite believe residents only rule imposed by the venue. On the day there were 3 sets of people for whom the finances were not a problem, but were not prepared to stay over:
1 . a couple whose child was ill, and although able to come to the wedding, were not prepared to leave the child overnight and therefore did not want to stay in the hotel.
- an elderly people who lived locally and wanted to get back home to their own bed (quite a common reason)
- a couple that had to work the next day, and again though able to attend the wedding, needed to leave to drive home that night.
Also there were quite a few people who did not want to stay, as their preference would have been to stay somewhere else, so they could have time and breakfast for themselves the next day, rather than continue to mingle with other guests from the wedding.
The above caused many arguments on the day as wedding guests were refused admittance, and tears from the bride who wanted the elderly couple (I think either her grandparents or a aunt and uncle) to see her married but were turned away because of not staying overnight.
The fallout from the above rages on many years later. And no I did not attend, because I could not afford the hotel's rates - though would have been able to attend had I been allowed to stay at a nearby Travel Lodge.
Good luck, OP, but I honestly feel if you go ahead you (or rather the venue) will create a lot of unhappy guests. YOU may have the perfect day, but your guests won't. I guess it comes down to priorities, is it more important to have what you want as a couple knowing you will upset many guests, or settle on another venue that may not have a spa/golf course but one in which your guests could enjoy the freedom of deciding whether to stay or not. It's a non brainer for me.