Maybe my simplistic view. Why can't you dispatch with two destination alternates as long as both of those satisfy the dispatch criteria?
If your dispatch calculation shows that you cannot land on the most favorable rwy in still winds but you can land on the rwy most likely to be assigned given the forcasted wind/weather conditions you can dispatch with two alternates that comply fully with the dispatch requirements. When doing this you need to perform a new calculation before landing with the latest weather reports available, and satisfy dispatch criteria on the runway assigned to you. If this calculation fail, even though your inflight assessment of a safe landing permits you to land, you are not legally allowed to land on that runway.
However; This exemption rule cannot be used if your destination have more than one runway.
If you can land on the most favorable rwy in still wind but not on the rwy most likely to be assigned given the forcasted weather conditions, you may dispatch with only one alternate complying fully with the dispatch requirements.
OPS 1.515
Landing — Dry runways
(a) An operator shall ensure that the landing mass of the aeroplane determined in accordance with OPS 1.475(a) for the
estimated time of landing at the destination aerodrome and at any alternate aerodrome allows a full stop landing from
50 ft above the threshold:
1. For turbo-jet powered aeroplanes, within 60 % of the landing distance available; or
2. For turbo-propeller powered aeroplanes, within 70 % of the landing distance available;
(b) When showing compliance with subparagraph (a) above, an operator must take account of the following:
1. the altitude at the aerodrome;
2. not more than 50 % of the head-wind component or not less than 150 % of the tailwind component; and
3. the runway slope in the direction of landing if greater than +/-2 %.
(c) When showing compliance with subparagraph (a) above, it must be assumed that:
1. the aeroplane will land on the most favourable runway, in still air; and
2. the aeroplane will land on the runway most likely to be assigned considering the probable wind speed and direction
and the ground handling characteristics of the aeroplane, and considering other conditions such as landing
aids and terrain.
(d) If an operator is unable to comply with subparagraph (c)1 above for a destination aerodrome having a single runway
where a landing depends upon a specified wind component, an aeroplane may be despatched if 2 alternate aerodromes
are designated which permit full compliance with subparagraphs (a), (b) and (c). Before commencing an approach to
land at the destination aerodrome the commander must satisfy himself/herself that a landing can be made in full compliance
with OPS 1.510 and subparagraphs (a) and (b) above.
(e) If an operator is unable to comply with subparagraph (c)2 above for the destination aerodrome, the aeroplane may be
despatched if an alternate aerodrome is designated which permits full compliance with subparagraphs (a), (b) and (c).