"At the outset, we must again make this preliminary statement: we do not abolish the Mass, but religiously keep and defend it. Masses are celebrated among us every Lord's Day and on the other festivals" (AC XXIV:1).
The observant reader of our Society's Rule will notice that the SSP is committed to promoting and encouraging both the weekly (every Lord's Day, i.e., every Sunday) celebration of the Sacrament of the Altar (Rule 4) and the observance and celebration of saints' days and commemorations (Rule 7), which is in line with what we Lutherans confess, as made clear in the quotation above.
As Dean of the SSP, I am engaged in several ongoing conversations with men who are interested in learning more about our Society. A question that keeps popping up within these conversations is: Are weekly Communion and the observance of saints' days prerequisites to joining the SSP?
No. These are not prerequisites. We have members who serve, or belong to, congregations that do not have either weekly Communion or observances of saints' days. Our Rule simply requires that our Society's members will promote and encourage these practices in their congregations. The expectation of our Society's members is that they will work toward restoring these practices, where they are not currently in place, through ongoing catechesis. We readily recognize that the restoration of these practices takes time and patience, varying from congregation to congregation, and so we do not place any time constraints upon our members to restore them, but simply trust that their voluntary commitment to our Rule means that they are promoting and encouraging these practices to the best of their ability and within whatever limitations their particular circumstances place upon them.
Having hopefully clarified where our Society stands on this, I'd like to add that I do believe that the restoration of observing and celebrating saints' days and commemorations can be accomplished without much opposition by most Lutheran pastors inclined to restore such. Do note that I said, "most." There are certainly some congregations where this might invoke severe opposition, but, in most of our congregations, I doubt that pastors have much to fear in this regard. There is a huge difference between changing what happens every Sunday (e.g., restoring weekly Communion where that is not currently in place) and adding Services during the week to observe and celebrate saints' days. While the former will certainly bring many challenges and some degree of opposition, the latter can usually be done without the raising of too many eyebrows. Do note that I said, "usually."
My advice to my fellow Lutheran pastors who wish to begin observing and celebrating saints' days and commemorations is: Just do it. Well, actually, don't just do it. Let people know you're going to do it. Teach them why you're going to do it. Show them how all our hymnals contain sanctoral calendars, and how the expectation of our Confessions is that we will celebrate Mass "on the other festivals." Then, just do it.
Actually, I should add one more caveat to my "just do it" advice: Don't require anyone else in the congregation to participate in the planning or implementation of these additional Services. In other words, be prepared to unlock the doors, turn up the heat or A/C, prepare the altar, change the paraments, and conduct the Service sans organist or elders or ushers or acolytes, etc. It may be that some of your parishioners will voluntarily step forward and offer their assistance with these additional Services, but, if you are prepared to do everything yourself, no one will be able to argue that these additional Services are placing an additional burden upon members of the congregation.
I have experience with this. I added the regular observance and celebration of saints' days where I serve back in 2006, a little over a year after beginning my service here as pastor, and received no opposition or complaints about it. I did have a couple of parishioners question me about it, as they had never heard of Lutherans observing saints' days (sad, that), but I simply showed them pages x-xiii in our then-new Lutheran Service Book hymnals, which includes a nice summary of why Lutherans observe saints' days on p. xii, and they were fine with it. Besides those couple inquiries, I heard nothing else. The beauty of adding additional Services like this is that those who may be opposed to them, for whatever reason, simply don't have to attend them. These Services are not forced upon anyone, but are simply added for those who wish to receive our Lord's Gifts at them, in addition to their regular reception of His Gifts every Lord's Day.
Our observance of saints' days where I am blessed to serve has evolved over the years. For the first few years, we simply stuck to the list of Feasts and Festivals on p. xi of LSB, and observed them on their actual days. Over time, we began to add some of the Commemorations (pp. xii-xiii), and eventually we went to a regular Wednesday evening schedule for our observance of Feast Days, moving the closest Feast Days/Commemorations to each Wednesday evening, which may not be the liturgical ideal, but has provided a consistency that allows more of our parishioners to attend them. We still observe every Feast and Festival listed on the sanctoral calendar in LSB annually, using not only Wednesday evenings, but also Thursdays at Noon, after our regular weekly Bible Study, when there are more Feasts/Festivals in a month than Wednesdays. But, we have also observed other Feasts/Festivals beyond those listed in LSB, using the sanctoral calendar provided in Daily Divine Service Book: A Lutheran Daily Missal, edited by Fr. Heath Curtis, which I've found to be an invaluable resource, as it provides all the propers one needs for all the Feasts and Festivals found therein. It really is an awesome resource and, as a bonus, you can even design your own custom cover:
Anyway, I really do think that most Lutheran pastors would be pleasantly surprised by the lack of grief they might be worried about getting in beginning the observance and celebration of saints' days. But, again, do note that I said, "most."