since plumbers have said "no problem" what you may want to know more clearly is what will really be involved. If so, you need to draw and post the drain pipe layout underneath the bathroom, and show where the joists are if this is not a concrete slab. Whether a toilet can be moved several feet away depends on where the vent is, and on the general layout which can be shown in a simple diagram, stick-drawn (a few straight lines) .
Looks like you are
1.) moving the tub drain a couple inches,
2.) either shortening or extending the toilet ("closet") "waste arm",
3.) adding a "continuous waste - end outlet" to the current sink drain,
4.) not changing the shower in any way.
The terms are the right ones to search on, if you want to know more first before asking for explanation.
edit: Master Plumbers who tell you they can do it, will be right 100% of the time. If any of the people you consulted where Master Plumbers, you can sleep well at night knowing that they have adequate professional training. What you can get here is more knowledge for yourself, and maybe a couple ideas about a couple minor things that can be overlooked at first glance.