Change niche of a domain

Hi,

I have actually a site I'm using as a landing page for my Amazon Affiliate Links from social media sites like Facebook.

Since the domain is a really nice one and easy to remember (brandable) I would like to take this domain and make a full dropship store on it instead of just use them as a amazon affiliate landing page.

I have like 200 pages indexed in google and I don't know what would happen when I change the site from today to tomorrow.

I would have still this pages indexed and I have also a "few" like 10-20 backlinks pointing to this domain but this backlinks wouldn't make sense on my "dropship store."

Should I change the niche of that nice brandable domain to a dropship store with different items than the actual "amazon landing page"?

As long as the products are somewhat related, there should be no problem. Gotta build new links for the new niche though, as the topic of the old links won't match.

Only problem is this sort of change usually takes a few weeks or even months. Google indexing is very slow lately, for some mysterious reason.

The products are related more or less since I promote(d) some general products and niche related. But the site is pretty much niche related not 100% but at least 70-80%.

I thought about this step because I have both domains .com and my TLD and the domain is nice brandable with 6 digits.

Since it was an Amazon Affiliate Shop I have a few categories and products that are not exists anymore. Google will deinxed them after a while. Will I get than a lot 404 errors since the products are deleted and I have about 200 index pages.

Should I just ignore them and wait until google know they are gone?

I've added two more related niches to my site, even though the website name has a keyword from the original niche in it. I also did a 301 redirect from an expired niche related domain which I built content on, which is related content to my main site. The site has really picked up since I added the two new niches and the 301. On the 18th March before one of the new niches was added I had 259 impressions and one click for US data only, on the 22nd April I had 522 impressions and seven clicks. Also a keyword which was stuck on page 2 from the original niche is position 8 for 5400 US searches and the best and reviews variants is number 1, 320 searches each for review/s.