You have a challenging situation. You feel like the "new people" can overpower you (and maybe the others), but this is based on perception. Then in your comments you mention that you are sometimes described as "over-assertive" but worry that is a misperception that the newcomers might assume is valid. Also, if you have experience and good ideas for long-term, strategic decisions for your company, but they get "shot down" in a single meeting, the meeting structure seems misaligned with it's purpose. So, here are a few suggestions:
- Take Notes and Keep Score
- Demonstrate that your ideas demand serious consideration
- Work toward changing the structure of the meetings
Take Notes and Keep Score
Your ideas may get shut down less often than others in the group. Focusing only on the response to your own ideas can create bias. Someone should be writing down the ideas presented and their disposition. If no one is doing that, start doing it yourself. Keeping track may help you feel like your ideas are better received than you realize (or maybe it will validate your concern). Also, documenting ideas that can be reviewed later will help you think more clearly about other proposals, etc. Also, others in your group may be more considerate if they feel like there responses are being "monitored" by your note-taking.
Demonstrate that your ideas demand serious consideration
If I were in these meetings with you, I would observe that your proposal is "shot down" like you have stated, but then I would be curious what happens next. Did you take notes to track and try to address the voiced concerns? Do you later provide research or data to refute invalid concerns? Are you a real "force to be reckoned with" or do you cower when faced with the opposition? Because someone that shoots down your ideas to look like a hot-shot in the moment during a meeting would take pause if they were worried that lack of careful consideration would haunt them.
Based on your intellect and experience, they should consider the political consequences when you revisit, and invalidate, their arguments in the next meeting based on evidence, anecdote or whatever. They should feel like arguments against your ideas should be presented with caution, not with disdain or guesswork. If you have good ideas and they are not being heard, then demand that they be heard by listening to concerns, recording them for your review and then providing evidence and data to dismantle the negativity of nay-sayers. Highlight that your ideas have value that demand consideration, discussion and attention.
In particular, if I see someone in a meeting that throws out ideas and then never revisits them or simply moves on to the next issue, I would be hard-pressed to become an advocate of anything they presented. But if someone presents an idea, listens to feedback and appropriately addresses concerns or criticisms, then I would be hard-pressed to challenge them. They should fear poorly constructed or rapidly dispensed criticism haphazardly thrown against your mental faculties and experience.
Work toward changing the structure of the meetings
Leadership meetings regarding corporate structure should deeply consider and evolve ideas from all participants tasked with that responsibility. Ideas should not be flippantly dismissed in a matter of moments. Not only is the company missing out on your good ideas, those that oppose you frequently may also have good ideas that you are probably not inclined to listen to closely or take as seriously as you should, given your emotional position on the reception of your own ideas.
The meetings should have structure that includes:
A) Urgent Matters
B) New insights or information on open issues/ideas from previous meeting(s)
C) Discussing new issues
D) Making decisions, if required
If you are given a problem and your ideas are shot down without further consideration, then the meeting format should include the recording of an idea that any member of the leadership team considers worthy of additional research or continued discussion to remain "open" until the group either reaches a consensus or else is forced to make a decision due to outside forces.
This kind of structure would invalidate any one individual being "shut out" by several others, while holding that individual accountable to the value of their ideas. If you feel strongly that your idea has merit, if only it were more thoroughly considered, then the meetings should be structured to support you - as well as others in your group that feel the same way about their own ideas.
Ultimately, it would be ideal if you could propose that the meeting be structured with an agenda like the one above, or another similar one, that requires an idea to be resurrected in a future meeting if any one of the members in the meeting deems it worthy or necessary. That allows the champion of the idea time to find support or better articulate the idea when others present opposing or negative positions. It removes their ability to bully ideas out of the discussion.
Hope this is helpful.